Alesis QuadraSynth Plus, Reference Manual

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MIDI Supplement: Appendix B
QuadraSynth Plus Piano Reference Manual 181
A
PPENDIX
B
MIDI S
UPPLEMENT
MIDI Basics
Most current electronic instruments and signal processors, including the
QuadraSynth Plus, 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 ensure compatibility of equipment between 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).
MIDI Hardware
MIDI-compatible devices usually include both MIDI In and MIDI Out jacks,
which terminate in 5-pin DIN-style 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.