ALESIS SR-16 - Manual (Page 66)

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CHAPTER 9: MIDI SUPPLEMENT
(This chapter is adapted with permission from Power Sequencing with Master Tracks Pro/Pro
4 and The Complete Guide to the Alesis HR-16 and MMT-8, copyright 1990 and 1989
respectively by AMSCO Publications.)
9.1 MIDI BASICS
Most current electronic instruments, including the SR-16, contain an internal computer.
Computers and music have been working together for decades, which is not surprising
considering music's mathematical basis (consider frequencies, harmonics, vibrato rates,
tunings, etc.). In the mid-70s, microcomputers became inexpensive enough to be built into
consumer-priced musical instruments. They were used for everything from sound generation
to storing parameters in memory for later recall.
In 1983, the MIDI (Musical Instrument Digital Interface) specification was introduced to better
exploit the computers inside these new musical instruments, primarily to insure compatibility
with equipment from other manufacturers. MIDI expresses musical events (notes played,
vibrato, dynamics, tempo, etc.) as a common "language" consisting of standardized digital
data. This data can be understood by MIDI-compatible computers and computer-based
musical instruments.
Before electronics, music was expressed exclusively as written symbols. By translating
musical parameters into digital data, MIDI can express not only the types of musical events
written into sheet music, but other parameters as well (such as amount of pitch bend or
degree of vibrato).
9.1A MIDI Hardware
MIDI-compatible devices usually include both MIDI in and MIDI out jacks, which terminate in
5-pin "DIN" connectors. The MIDI out jack transmits MIDI data to another MIDI device. As you
play a MIDI controller such as a keyboard, data corresponding to what you play exits the MIDI
out jack. Example: if you play middle C, the MIDI out transmits a piece of data that says
"middle C is down." If you release that key, the MIDI out transmits another piece of data that
says "middle C has been released." If the keyboard responds to the dynamics of your playing,
the note data will include dynamics information too. Moving the modulation wheels and
pedals attached to many synthesizers will also generate data associated with the wheel or
pedal being used.
The MIDI in jack receives data from another MIDI device. In addition to the type of
performance data described above, rhythmically-oriented MIDI devices (e.g., drum machines)
can often transmit and/or receive additional MIDI timing messages that keep other
rhythmically-oriented units in a system synchronized with each other.
An optional MIDI thru jack provides a duplicate of the signal at the MIDI in jack. This is handy
if you want to route MIDI data appearing at one device to another device as well. The SR-