588 lines
40 KiB
Plaintext
588 lines
40 KiB
Plaintext
MIDI for the Computerphile Page 1
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A MIDI Primer for Computerphiles
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In the course of pursuing my dual interests in music and
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computers, I've noticed one thing: though "crossover" in these
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two fields is certainly evident in hardware and software, most
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computer folk seem to know little about what those weird musician
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types are doing with their digital machines, and musicians, well,
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many musicians still think a byte is something you go out for
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after playing a set. Hopefully, this report will be of some use
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to computer people who would like to know something about the
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computer revolution which has swept the music industry, but don't
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know where to start. Obviously, this is a very large topic, and
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I can only present the broadest outlines here. If there is
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sufficient interest, more detailed reports will follow.
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A Basic Definition and a Little History
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MIDI (Musical Instrument Digital Interface) is a
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communications protocol developed jointly by American and
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Japanese manufacturers of electronic musical instruments. It is
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a defined standard administered by an independent association,
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the International Midi Association, and, at least theoretically,
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assures compatibility among equipment produced by different
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manufacturers. In practice, the ideal of total compatibility is
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not always achieved, but at least "MIDI standard" has a little
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more meaning than "RS232 standard interface".
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Now for a little history. MIDI is a fairly recent
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innovation; the standard was first proposed in 1981, when,
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fortunately, it was realized that unless someone did something,
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chaos would prevail in the musical instrument industry (with, of
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course, the resultant loss of sales. Never forget that MIDI was
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spawned by manufacturers, not by users. More on this later.)
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Over the past 15 or 20 years, many electronic instruments
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have been introduced. Keyboard synthesizers are examples that
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are probably familiar to most people. These machines were analog
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devices -- the pitch of the sound they produced was determined by
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a linear-scaled control voltage generated by the keyboard. With
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the advent of microprocessors, it became feasible to produce
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digitally controlled instruments, eliminating the inherent
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instability and inaccuracy of the analog control approach.
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Please note, that the terms digital and analog are used here only
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to describe the method of control; they have a totally different
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meaning when applied to the technique used to generate the sound.
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That will be discussed in the section on Hardware. Anyway, what
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is important is that instead of keyboards that produced varying
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voltages, you now have keyboards that produce discrete codes,
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just like a computer keyboard.
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Now I must digress for a moment, and present a short
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discussion on the elements of tonal music. Tonal music (as
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distinguished from atonal music, i.e. noise) can be described as
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constituting three determinant parameters:
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1 - Notes (comprised of pitch and harmonic data)
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2 - Volume (how loud or soft the sounded note is)
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3 - Duration (how long the note is sounded)
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A digitally-encoded keyboard is capable of generating, as a
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discrete quantity, only one of the 3 parameters. Notes are
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determined by which key is pressed. However, duration can be
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determined by measuring how long the key is pressed against a
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known time base. Volume is a little tougher; you can measure the
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pressure with which the key is hit, but that will necessarily
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require analog measurement. However, if you measure the time
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between the moment the key begins to be depressed and the moment
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it is fully depressed, you will know how fast the key is
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travelling, which gives a good indication of how hard it was
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struck. This measurement, (beginning of key travel - end of key
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travel/time) is called "velocity" and provides the third
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parameter. (Some MIDI instruments use analog pressure
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measurements to generate velocity data).
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If these three parameters were recorded in real-time, and
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then transmitted to an instrument, it would be possible to
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reproduce the original performance exactly as the musician played
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it. This technique offers a major advantage over analog
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recording technology: there is none of the degradation of sound
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which is inherent in any analog recording process. The first
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devices which attempted to store and reproduce these parameters
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are familiar to everyone: the old-fashioned player piano
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captured key presses in real-time and stored them on paper piano
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rolls for later retrieval. The evolution of electronic
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instruments resulted in various schemes to electronically store
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these parameters. However, the early attempts at "sequencing"
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(the process of coding, storing and retrieving note, volume and
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duration data) were individually developed by each manufacturer
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-- compatibility between different brands of instruments was rare
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(nonexistent).
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The MIDI standard was originally proposed to provide a
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single standard to be used by all instrument manufacturers, so
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that varied and different instruments could function together.
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However, as will be shown later, MIDI has evolved considerably
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beyond a basic note definition "language".
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A Little Technical Data
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I won't reproduce the full standard here because it is
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readily available from a variety of sources and is not necessary
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for understanding the basic principles and applications of MIDI.
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MIDI is a synchronous digital protocol. Data is sent in 8-bit
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words at 31.2K baud using a current loop. Why yet another
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format, when good ole' RS232 is sitting there on just about every
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computer in existence? The official Party Line is: RS232, with
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its top speed of 19.2K is too slow to handle all the note data.
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Current loop is necessary to suppress interference that would
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result from the long cable runs. Could it be an excuse to sell
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more hardware? Hmmmmmm. Anyway, back to facts. MIDI protocol
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consists of control and data words which may be from 1 to 3 bytes
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long, or, in certain situations, longer. MIDI defines the three
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parameters from the previous section as follows:
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NOTES: 128 notes are defined, from 0 to 127. Notes
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follow the standard even-tempered chromatic scale.
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Notes are NOT defined as specific frequencies,
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permitting performers to tune their instruments as
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required.
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VOLUME: The primary means of specifying volume is
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velocity (see previous discussion). Velocity is
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quantized per note in discrete steps from 0 (softest)
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to 127 (loudest). There are also other parameters
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which control relative volume of the entire instrument.
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DURATION: MIDI handles duration of notes with two
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parameters: NOTE ON and NOTE OFF. NOTE ON is
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generated when the key is pressed, NOTE OFF is
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generated when the key is released. These two commands
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are sent independently of each other; if a NOTE ON is
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issued and a corresponding NOTE OFF is not sent
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(because of data errors, mechanical failures, or poor
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programming) the note will sound forever (or until the
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instrument is turned off). This presents occasional
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problems, particularly in live performance, because, as
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in any communications protocol, data errors do
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sometimes happen. MIDI does provide an "All Notes Off"
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command.
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As stated before, duration must be measured against a known
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time standard. MIDI provides a MIDI clock signal, which is sent
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as a specifically designated data byte. MIDI divides each
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musical beat into 128 MIDI clocks. MIDI also defines the
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following parameters:
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PROGRAM CHANGE: This parameter selects different
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"patches" or sounds in the musical instrument. The
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programs are numbered 0-127. Note that the patches
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themselves are not defined by the MIDI standard.
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Program #32 might be a violin on one synthesizer and
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barking dogs on another.
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CHANNEL: MIDI provides for 16 different channels.
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Most MIDI commands and data can be specific to a single
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channel, i.e. instrument, or can be global.
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PITCH BEND: As the name implies, the pitch of the note
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can be "bent" up or down in real time (remember Jimi
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Hendrix?).
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MODULATION: This is a control parameter that usually
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effects the vibrato sound of the note, though some
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instruments can be programmed to use modulation data to
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control other parameters. Modulation and Pitch Bend
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are usually controlled from the instrument with wheels
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or levers that the performer can rock back and forth.
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SUSTAIN: The same as the sustain pedal on a piano, it
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will cause the note to sound until the pedal (or other
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control device) is released.
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The MIDI spec allows for 127 different control parameters,
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although only a small number are currently identified and
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standardized. In addition, MIDI provides a "system exclusive"
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message. Each manufacturer is assigned their own unique "sys ex"
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code which allows them to implement custom features without
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interfering with other manufacturers customizations. Ah ha! you
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say, doesn't that defeat the purpose of a "standard"? Yes, to an
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extent it does, but remember it was the manufacturers of the
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equipment who pushed for a standard, and allows for innovation
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and differentiation between brands. And, as stated earlier, you
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must admit that this standard is considerably more consistent
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than a "standard" RS232 interface.
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The preceding constitutes only the broadest description of
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the MIDI protocol, and there are quite a few more features which
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I haven't covered here. However, you should have a general idea
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of the kinds of data MIDI can handle. Now I'll tell you some of
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the ways MIDI is used.
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What is MIDI Used For?
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Ok, we've established that MIDI is both a communications
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protocol and note definition language. What can it do?
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1. Control of Instruments
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Any musical instrument can be thought of as having two
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distinct components: the sound producing component and the
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control component. As an example, the keyboard of a piano, the
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frets on a guitar and the buttons on a clarinet can all be
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thought of as control components. The piano's strings and
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hammers, the guitar's strings and acoustic body (or magnetic
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pickups if it is electric) and the clarinet's reeds and hollow
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body are all sound producers. The first application for MIDI
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permits the separation of control and sound production
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components. The most common (though not the only) MIDI
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controller is the keyboard. The keyboard generates the NOTE ON
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and NOTE OFF data as well as various other control data (see
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previous section) and passes it on to the sound producing
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section. The sound producing section could be a synthesizer,
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digital sampler, drum machine, or any other MIDI equipped sound
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producing device. Most synthesizers combine the sound producing
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device and the keyboard controller in a single physical package.
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However, MIDI permits them two be addressed as two distinct and
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separate sections.
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A single musician at a single keyboard can play many
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different instruments simultaneously. There are two ways of
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doing this. The first places several different sound producers
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on the same channel, all responding to the same MIDI data at the
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same time. This is a process called "layering" and can be used
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to produce full, rich, harmonically complex sounds. The effect
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is of several different instruments all playing in unison.
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The second technique is called "splitting" the keyboard --
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arbitrarily assigning specific channels to specific notes on the
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keyboard. This permits different instruments to play different
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music, all under the control of one musician at one keyboard. As
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an example, the musician might assign the bottom two octaves of
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the keyboard to channel 1 and the rest of the keyboard to channel
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2. If a digital sampler set to reproduce the sound of a bass is
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assigned to channel 1, and a synthesizer producing a piano sound
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is assigned to channel 2, the musician will be able to play the
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bass line accompaniment with his left hand while playing the
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piano lead with his right.
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Note that when instruments are layered, an unlimited number
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of instruments may be played. However, when the keyboard is
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split, the maximum number of instruments that may be controlled
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is limited to the maximum number of MIDI channels -- 16.
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2. Sequencers
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Another obvious application for MIDI is the storing of the
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MIDI data stream for later playback -- a process known as
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sequencing. This task may be performed either by a dedicated
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piece of hardware (called, of course, a "sequencer") or by
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general purpose computers equipped with the appropriate software
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and interfacing.
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Most sequencers allow editing of the MIDI data -- wrong
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notes can be corrected, new material can be entered one note at a
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time, and sections can be rearranged, moved or copied (much like
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a word processor). Almost all sequencers allow for transposition
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(changing key) and tempo changes. Some will "auto-correct" so
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that all notes are played exactly on the beat, eliminating any
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sloppiness in playing.
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Since MIDI provides 16 unique channels, 16 different
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instruments can be controlled simultaneously, allowing the
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sequencer to function like a multi-track tape recorder. Each
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instrument is "played" into the sequencer individually on a
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different channel. When all the parts have been entered, the
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sequencer can play them back all at the same time, in effect
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creating a one-man band (or one-man philharmonic orchestra).
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Finally, since MIDI was developed as a professional and
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semiprofessional musical tool, several features required for
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recording are supported. Most sequencers allow for some form of
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tape sync. In the most basic form of tape sync, the sequencer
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provides a synchronization signal which can be laid down on one
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track of a multi-track tape recorder. When new tracks are laid
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down, the sequencer can synchronize to the previously recorded
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material. This makes multi-track recording, over-dubbing, and
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similar recording tricks much easier. The MIDI spec also defines
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a MIDI SONG POINTER, which can be thought of as "mile markers" in
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the music. A sequencer that supports MIDI SONG POINTERS is
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capable of automated punch-in and punch-out -- the process of
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inserting new material into a previously recorded track.
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3. Librarian Software
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One of the uses manufacturers of MIDI instruments make of
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the SYSTEM EXCLUSIVE command is for data dumps; literally
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"dumping" all the parameter data needed to define sounds and
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setups out the MIDI line on command. Software that stores this
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data for later recall is called Librarian software. Most
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librarians are not limited to merely storing and retrieving the
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dumped data, but are also capable of editing specific patch
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parameters -- a task which is more easily performed on a computer
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with a full keyboard and video display than on the more limited
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displays and entry devices available on the synthesizers
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themselves.
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A special form of librarian, generally called a Sound
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Modeling Program, use the SYSTEM EXCLUSIVE dump command to obtain
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wave sample data from digital samplers (see the section on
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Hardware). The wave sample can then be displayed, manipulated,
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stored and retrieved by the librarian. "Serious" sampling with
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digital samplers virtually mandates the use of some form of Sound
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Modeling Program.
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4. Notation Software
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Notation software takes the MIDI note data and translates it
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into conventional music notation which can be displayed on the
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screen or printed on a dot matrix or laser printer. It allows a
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musician to play music in on the controller keyboard in real time
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and get finished musical scores out. Alternatively, music can be
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entered in notational form on the computer keyboard using
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wordprocessor-like commands, and the finished result can be heard
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played on a MIDI equipped synthesizer.
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Copyright 1987 by Paul Tauger. This article may be freely
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exchanged, copied and/or distributed provided it is done without
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charge.
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5. Other Applications
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Lately, MIDI has also found application in non-musical
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functions, e.g. controlling mixing boards, stage lighting and
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sound processing equipment (reverbs, digital delays, etc.).
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Problems with MIDI
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As powerful a tool as MIDI is, it is not totally without
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problems. What follows are a few cautionary notes:
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1. As already mentioned, MIDI defines note duration with two
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separate data commands: NOTE ON and NOTE OFF. The possibility of
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a NOTE ON being transmitted without a corresponding NOTE OFF
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following is an always present danger. Data can get garbled
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during transmission, lines become unplugged (the MIDI standard
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utilizes 5-pin DIN connectors which have a nasty habit of
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loosening in their sockets), channels accidentally get switched,
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etc. Without a NOTE OFF command, the note will continue to sound
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for ever. This can be a major annoyance in a recording session
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(more than annoying if it occurs during that once-in-a-lifetime
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hot set) and in live performance, well, you get the idea.
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Various manufacturers have come up with different solutions to
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the problem, the most common being a button which, when pressed,
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produces an ALL NOTES OFF command. This will, of course, silence
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the offending note, but silences all the other notes in the
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process. Because the two note NOTE ON/NOTE OFF structure is
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intrinsic to the MIDI spec, we will just have to live with the
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occasional stuck note.
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2. MIDI transmits at 31.2k baud. A little math shows that MIDI
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is capable of sending approximately 1000 notes per second. This
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is obviously more than any musician can ever play. However, when
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you divide this capacity among 16 channels, add in the data
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stream produced by controllers such as pitch benders and
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modulation wheels, then throw in a few program changes for good
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measure, you have the possibility of overrunning the data. To be
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honest, I've never heard of this happening, but the possibility
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is still there.
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3. Most MIDI instruments contain a MIDI-in jack for receiving
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data, a MIDI-out jack for transmitting data, and a MIDI-thru jack
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for passing MIDI data along to another instrument. When
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instruments are daisy-chained together, a perceivable delay
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develops between the first and last instrument in the chain.
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This is the infamous "MIDI delay" of which you may have heard.
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This delay can be eliminated by using a device known as a "MIDI
|
||
|
||
Thru Box". This is an active splitter that accepts one MIDI
|
||
|
||
input and divides it into 4,6 or more MIDI outputs, thereby
|
||
|
||
assuring that all instruments receive the MIDI signal at the same
|
||
|
||
time. Does it solve the problem? You bet! Does it cost more
|
||
|
||
money? You bet!
|
||
|
||
4. Another problem, frequently mistaken for MIDI delay, is
|
||
|
||
inherent in some MIDI synthesizers. Remember that the keys on
|
||
|
||
the keyboard are scanned sequentially, in the same manner as a
|
||
|
||
computer keyboard. In some brands of keyboard synthesizers, the
|
||
|
||
internal electronics introduce their own delays in translating
|
||
|
||
the key presses into sounds. Though not specifically a MIDI
|
||
|
||
problem, it is a problem none the less, and is particularly
|
||
|
||
evident when the musician "grabs" large chords consisting of many
|
||
|
||
notes. Fortunately, this problem is recognized as a hardware
|
||
|
||
"bug" and is usually corrected by the manufacturer (after enough
|
||
|
||
people complain).
|
||
|
||
5. By its very nature, MIDI is designed to permit one controller
|
||
|
||
on line at a time. More than one controller on line will result
|
||
|
||
in inevitable data collisions with the resultant garbling of
|
||
|
||
data. Think of two computers sending data to two printers at the
|
||
|
||
same time. There are devices available which mediate data
|
||
|
||
contention between two MIDI controllers. Generally called Midi
|
||
|
||
Mergers, they are another relatively expensive solution to what
|
||
|
||
seems like a simple problem.
|
||
|
||
6. Though the MIDI protocol is clearly defined in the spec,
|
||
|
||
computer storage schemes are left up to the individual software
|
||
|
||
producer. There is no MIDI equivalent of an ASCII or EBDIC file.
|
||
|
||
Consequently, MIDI data files produced by one piece of software
|
||
|
||
can not be read by another. This would be fine if there were
|
||
|
||
such a thing as a program that did everything (and did it well).
|
||
|
||
However, as in the case of the "integrated" packages that
|
||
|
||
combined word processors, spread sheets, data bases and
|
||
|
||
communications software all in one box, such as thing simply
|
||
|
||
doesn't exist. Right now, the only way to exchange MIDI data
|
||
|
||
between programs is by transmitting the data over a physical MIDI
|
||
|
||
data line between two computers.
|
||
|
||
7. As mentioned earlier, the MIDI spec provides considerable
|
||
|
||
latitude to manufacturers who want to incorporate custom features
|
||
|
||
in their instruments. Consequently, MIDI is afflicted with
|
||
|
||
"creeping non-standardization". There are already controller
|
||
|
||
number conflicts between some of the largest instrument
|
||
|
||
manufacturers, and the SYSTEM EXCLUSIVE command guarantees that
|
||
|
||
no single librarian program will work with all synthesizers.
|
||
|
||
8. Now for what I see as the major problem with MIDI - MONEY!
|
||
|
||
Until the electronic revolution, quality musical instruments were
|
||
|
||
carefully crafted, often handmade, and very expensive. After
|
||
|
||
all, great instrument making is an art. Consequently, musicians
|
||
|
||
have become accustomed to paying a lot of money for the
|
||
|
||
instruments they play. This tradition has been maintained by
|
||
|
||
many manufacturers of mass-produced electronic instruments.
|
||
|
||
There are exceptions (see the description of the Casio CZ-101 in
|
||
|
||
the Hardware section), but for the most part, the sales price of
|
||
|
||
a piece of electronic musical gear frequently does not bear any
|
||
|
||
correspondence to the cost of its manufacture. Fortunately, the
|
||
|
||
current trend is towards dropping prices. However, walk into any
|
||
|
||
music store and you will see MIDI cables (2 DIN plugs and 10 feet
|
||
|
||
of 2 conductor shield cable) for $25 or more. Though good MIDI
|
||
|
||
software tends to be very expensive, it should be remembered that
|
||
|
||
MIDI software publishers have a much more limited market for
|
||
|
||
their product than publishers of more common business-oriented
|
||
|
||
packages.
|
||
|
||
A Brief (and Biased) Hardware Catalog
|
||
|
||
I would like to conclude this report with a description of
|
||
|
||
the types of MIDI hardware currently available. Hardware
|
||
|
||
selection is a very personal decision, and what I say here
|
||
|
||
(beyond the basic descriptions) is necessarily biased by my own
|
||
|
||
preferences. Here goes:
|
||
|
||
1. Sound Producing Devices
|
||
|
||
The devices which produce the actual sounds can be divided
|
||
|
||
into two basic categories:
|
||
|
||
- Synthesizers - devices which generate basic sound
|
||
|
||
waveforms, and, by manipulating various parameters of
|
||
|
||
the sound (envelope, modulation, etc.) can produce a
|
||
|
||
diversity of tonal textures and colors.
|
||
|
||
- Samplers - devices that digitally record, or sample,
|
||
|
||
a sound, and then play it back at pitches determined by
|
||
|
||
the controller.
|
||
|
||
Synthesizers can be divided into two broad categories.
|
||
|
||
Analog synthesizer use conventional oscillators and filters to
|
||
|
||
produce different sound waveforms, e.g. sine waves, square waves,
|
||
|
||
triangle waves, etc. Digital synthesizers "store" a digitally
|
||
|
||
encoded waveform in ROM, and produce their sounds by reading the
|
||
|
||
waveform out to D-to-A convertor. Generally, analog synthesizers
|
||
|
||
are thought of as producing "warmer" sounds than their digital
|
||
|
||
counterparts. Some common synthesizers are:
|
||
|
||
Yamaha DX-7 (approx. $1700) - The DX-7 has become something
|
||
|
||
of a "standard" for digital synthesis, and is used by many
|
||
|
||
professional musicians. Most librarian software supports
|
||
|
||
this machine.
|
||
|
||
Casio CZ-101 (approx. $300) - Casio has a complete line of
|
||
|
||
digital synthesizers, but the CZ-101, in my opinion, offers
|
||
|
||
more "bang for the buck" than anything else on the market.
|
||
|
||
This machine is supported by many librarians, is capable of
|
||
|
||
producing an astonishing range of sounds and is an excellent
|
||
|
||
"starter" for anyone interested in testing the waters of
|
||
|
||
electronic music. Two drawbacks: it has a small keyboard
|
||
|
||
that is difficult to play, and does not support note
|
||
|
||
velocity; all notes default to a velocity of 64.
|
||
|
||
Samplers are available in a wide range of prices and
|
||
|
||
capabilities. Factors to be considered in purchasing a sampler:
|
||
|
||
1 - Sample width. The more bits per sample, the better the
|
||
|
||
resolution, dynamic range, and fidelity. This rule is not
|
||
|
||
written in stone, however, as many manufacturers have
|
||
|
||
developed data compression algorithms that allow them to
|
||
|
||
squeeze more information out of smaller width samples, and a
|
||
|
||
12-bit machine may not necessarily sound better than an
|
||
|
||
8-bit machine.
|
||
|
||
2 - Sampling rate. Higher sampling rates permit the
|
||
|
||
reproduction of higher frequency sound data. The Nyquist
|
||
|
||
rule specifies a sampling rate 2-1/2 times the frequency of
|
||
|
||
the highest sound to be sampled, i.e. to sample the full
|
||
|
||
audible audio spectrum (20 Hz to 20,000 Hz), a sampler
|
||
|
||
should have a sampling rate of (2.5 * 20,000) or 50,000
|
||
|
||
samples per second.
|
||
|
||
3 - Number of active samples. The sound of a "real"
|
||
|
||
instrument can not be reproduced by sampling only one note
|
||
|
||
and "stretching" it across the entire keyboard. Many
|
||
|
||
samples taken at many different pitches are necessary to
|
||
|
||
effectively simulate the distinctive voice of an instrument.
|
||
|
||
Some samplers provide only a single sample at a time which
|
||
|
||
must be stretched. Others provide as many as 64 active
|
||
|
||
samples at a time which may be assigned to specific sections
|
||
|
||
of the keyboard as needed.
|
||
|
||
4 - Available memory. Samplers with a lot of memory can
|
||
|
||
allow higher sampling frequencies, longer samples, and more
|
||
|
||
active samples.
|
||
|
||
Digital Samplers are "where the action is" and new machines
|
||
|
||
are being introduced all the time. Some inexpensive samples of
|
||
|
||
samplers:
|
||
|
||
Akai S612 (approx. $1000 with disk storage): The least
|
||
|
||
expensive "real" sampler (as contrasted with several
|
||
|
||
sampling toys that have recently hit the market) the S612 is
|
||
|
||
also available in an expanded version called the S900 for
|
||
|
||
approximately $3000. The S612 is limited to one active
|
||
|
||
sample at a time. Sampling rate is also limited, which
|
||
|
||
restricts its ability to sample high frequency sounds. In
|
||
|
||
addition, it is a rack-mounted device which requires a MIDI
|
||
|
||
keyboard to control it. It is, however, a fully implemented
|
||
|
||
sampler for a minimum price, and constitutes a good
|
||
|
||
entry-level machine for those who want to experiment with
|
||
|
||
sampling.
|
||
|
||
Ensoniq Mirage (approx. $1700 with keyboard): The Mirage is
|
||
|
||
a versatile instrument that offers a user-selectable sample
|
||
|
||
rates up to 30 kHz with up to 16 active samples. The machine
|
||
|
||
also has a full sound modification section consisting of the
|
||
|
||
traditional envelope and filter synthesizer controls,
|
||
|
||
permitting the user considerable flexibility in customizing
|
||
|
||
sound samples. Ensoniq offers a large library of factory
|
||
|
||
samples on 3-1/2" disk (disk drive included with the Mirage)
|
||
|
||
which range in quality from adequate to extraordinary. A
|
||
|
||
good test for a sampler is the ability to recreate the sound
|
||
|
||
of an acoustic piano, as pianos produce extremely complex
|
||
|
||
waveforms. The Mirage does a very credible job with pianos,
|
||
|
||
as well as other acoustic instruments. The Mirage is also
|
||
|
||
available in a less expensive rack mount version (no
|
||
|
||
keyboard).
|
||
|
||
Sequential Circuits Prophet 2000 (approx. $2500): 12-bit
|
||
|
||
sampler with extensive MIDI implementation. Sampling rate
|
||
|
||
user-switchable up to 41 kHz. There has been some criticism
|
||
|
||
of the quality of factory-produced library samples, but the
|
||
|
||
machine is capable of extremely high-quality sampling.
|
||
|
||
Emu Emulator II (approx. $8000): A very high quality
|
||
|
||
sampler the uses a proprietary data encoding scheme to
|
||
|
||
purportedly wring 14-bit resolution out of 8-bit samples.
|
||
|
||
The Emulator was one of the first "affordable" samplers (as
|
||
|
||
compared with the $50K - $100K Fairlight and Synclavier) and
|
||
|
||
has seen extensive use in professional recording and live
|
||
|
||
performance.
|
||
|
||
Drum machines are specialized devices that simulate the
|
||
|
||
sound of a drum set. The sounds are ROM-based digital samples,
|
||
|
||
though some machines permit the user to sample their own sounds.
|
||
|
||
All drum machines allow the user to define a number of patterns
|
||
|
||
which can be strung together to form "songs". A representative
|
||
|
||
drum machine:
|
||
|
||
Yamaha RX-15 (approx. $400) - Has 16 different drum sounds
|
||
|
||
(only 12 available at the same time), memory for up to 99
|
||
|
||
patterns and 10 songs (depending on complexity). Good MIDI
|
||
|
||
implementation, though incapable of MIDI sys ex dumps. Also
|
||
|
||
available as the RX-11 (approx. $700) with complete MIDI
|
||
|
||
implementation.
|
||
|
||
2 - Keyboard Controllers
|
||
|
||
Keyboard controllers produce no sounds by themselves but
|
||
|
||
generate the MIDI data necessary to control MIDI sound-producing
|
||
|
||
devices. Keyboard controllers have "actions" that provide a feel
|
||
|
||
similar to traditional pianos.
|
||
|
||
MIDI data can also be generated by non-keyboard devices,
|
||
|
||
including guitars, drums and various wind instruments. Devices
|
||
|
||
called "pitch riders" can translate an analog sound input into
|
||
|
||
MIDI data output.
|
||
|
||
3 - Computers
|
||
|
||
This is a volatile area for discussion, with proponents of
|
||
|
||
different brands fiercely loyal to their machines (as I am
|
||
|
||
fiercely loyal to mine - an IBM PC-XT). Anyway, here's a quick
|
||
|
||
run down:
|
||
|
||
Inexpensive Machines:
|
||
|
||
Commodore 64/128: Many software packages are available, as
|
||
|
||
well as different interface options. The machine's 64K of
|
||
|
||
memory presents a limitation for sequencing and scoring
|
||
|
||
programs, but low cost of the Commodores makes for them good
|
||
|
||
MIDI "starter" systems. If you are considering the
|
||
|
||
Commodore, avoid software that claims it can use the 64's
|
||
|
||
internal sound chip to produce "real professional
|
||
|
||
synthesizer sounds". The sound chip on the 64 is quite
|
||
|
||
clever and very versatile, but is limited to three voice
|
||
|
||
polyphony and has severely restricted sound modifying
|
||
|
||
capabilities. It is not a substitute for a synthesizer by
|
||
|
||
itself. Passport and Dr. T are two publishers of quality
|
||
|
||
MIDI software for the Commodore.
|
||
|
||
Low-cost Atari's: Same limitations as the Commodore, though
|
||
|
||
perhaps with fewer quality software packages available.
|
||
|
||
Noted exception: Hybrid Arts produces well recognized and
|
||
|
||
well respected software, though unfortunately, only for the
|
||
|
||
Atari line.
|
||
|
||
Apple II - About on a par with the cheap Atari's from a
|
||
|
||
music standpoint. 48K memory presents severe limitations.
|
||
|
||
Moderately Priced Machines:
|
||
|
||
Only two worth considering - the Amiga and the Atari ST.
|
||
|
||
The Atari has slightly more software packages available and
|
||
|
||
offers a built-in MIDI interface. The MIDI interface is an
|
||
|
||
extra-cost option on the Amiga. I'll avoid jumping into the
|
||
|
||
Atari vs. Amiga war by saying both machines offer good value
|
||
|
||
and are well-suited for MIDI and other music applications.
|
||
|
||
More Expensive Machines:
|
||
|
||
Macintosh: In fairness, I must confess to a certain amount
|
||
|
||
of anti-Mac prejudice. My criticisms are not new:
|
||
|
||
expensive peripherals, up-until-recently closed
|
||
|
||
architecture, hard-to-support serial bus, operating system
|
||
|
||
designed for computerphobes, etc. However, if you like it
|
||
|
||
you like it, and there are some excellent professional music
|
||
|
||
packages available for it. However, my preference, hands
|
||
|
||
down, is:
|
||
|
||
IBM PC-XT (and PC clones): The PC offers a great variety of
|
||
|
||
powerful, professional music software packages, and a
|
||
|
||
variety of flexible MIDI interfaces are available for it.
|
||
|
||
It is also the only machine which will run Personal
|
||
|
||
Composer, the only notation program I've seen which actually
|
||
|
||
works. There are other notation programs out, but they are
|
||
|
||
so riddled with bugs as to be almost unusable, or else are
|
||
|
||
so limited in their implementations as to impose severe
|
||
|
||
restrictions on composers. (I will happily retract the
|
||
|
||
preceding statements upon compelling evidence to the
|
||
|
||
contrary). One program worth mentioning is Texture, a
|
||
|
||
sequencer which has become the de facto standard of
|
||
|
||
professional musicians.
|
||
|
||
Final Words
|
||
|
||
As stated at the outset, MIDI is a very large topic to be
|
||
|
||
tackled in a single report. I hope I have presented enough
|
||
|
||
information to give the MIDI neophyte a basic understanding of
|
||
|
||
the topic. Let me also remind you that the "review" material
|
||
|
||
presented here is highly subjective, particularly in the
|
||
|
||
"hardware" section. There are many more fine instruments and
|
||
|
||
software packages which I have not mentioned here.
|
||
|
||
A good source for information on MIDI and electronic music
|
||
|
||
in general is KEYBOARD magazine, which publishes reviews of
|
||
|
||
hardware and software, features on all aspects of keyboard music
|
||
|
||
(both acoustic and electronic), occasional how-to articles, etc.
|
||
|
||
I hope some of you who read this will be motivated to
|
||
|
||
experiment with MIDI. The control capabilities of sequencers and
|
||
|
||
the sound generating abilities of the various synthesizers and
|
||
|
||
samplers put the ability to create professional sounding music in
|
||
|
||
the hands of almost anyone. If there is enough interest, I can
|
||
|
||
prepare occasional reports that explore specific areas of
|
||
|
||
electronic music production in greater detail. Messages for me
|
||
|
||
can be left at The Sleepy Hollow BBS, 213-859-9334 (24 hours,
|
||
|
||
1200 baud, 8-bit, no parity, 1 stop bit), which, incidentally, is
|
||
|
||
the finest BBS I've encountered and is run by a knowledgeable and
|
||
|
||
dedicated Sysop.
|
||
|
||
|
||
Copyright 1987 by Paul Tauger. This article may be freely
|
||
|
||
exchanged, copied and/or distributed provided it is done without
|
||
|
||
charge.
|
||
|