System Common Messages - Alesis GT Reference Manual

of channels, usually to one.
The "mono/poly" message deals with voice assignment within the
synthesizer. In Mono mode, only one note at a time plays in response to
voice messages; in Poly mode, as many voices can play notes as are
available to play notes.
The QuadraVerb GT implements two different MIDI modes.
Omni On/Poly (Mode 1) The QuadraVerb GT responds to MIDI data
occurring on any channel.
Omni Off/Poly (Mode 3) The QuadraVerb GT is tuned to a single MIDI
channel, from 1 to 16.

8.5 SYSTEM COMMON MESSAGES

Intended for all units in a system, some of these messages are:
Song Position Pointer This indicates how many "MIDI beats" (normally
a 16th note) have elapsed since a piece started (up to 16,384 total beats). It
is primarily used to allow different sequencers and drum machines to
auto-locate to each other so that if you start one sequencer, the other
device will automatically jump to the same place in the song,
whereupon both continue on together.
System Exclusive This message (called sys ex for short) is considered
"exclusive" because different manufacturers send and receive data over
MIDI which is intended only for that manufacturer's equipment.
Example: Sending an QuadraVerb GT message to an Ensoniq SD-1 won't
do anything but the message will be understood by other QuadraVerb
GT. This data often contains information about individual instrument
programs.
Timing Clock A master tempo source (such as a sequencer) emits 24
timing messages (clocks) per quarter note. Each device synchronized to
the sequencer advances by 1/24th of a quarter note when it receives the
clock message, thus keeping units in sync after they've both started at the
same time. Many devices subdivide this clock signal internally for
higher resolution (e.g., 96 pulses per quarter note).
Start Signals all rhythmically-based units when to start playing.
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