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MIDI Supplement: Appendix B
QuadraSynth Plus Piano Reference Manual 185
System Common Messages
Intended for all units in a system, some of these MIDI 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 a QuadraSynth Plus message to an Alesis D4 Drum
Module won’t do anything, but the message will be understood by other
QuadraSynth Plus. 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.
Stop. Signals all rhythmically-based units when to stop playing.
Continue. Unlike a Start command, which re-starts a sequencer or drum
machine from the beginning of a song each time it occurs, sending a
continue message after stop will re-start units from where they were
stopped.
General MIDI
General MIDI is an extension of the MIDI standard designed to meet the
demands of the ever-growing multimedia industry, and to make simple the act
of playing commercially produced MIDI sequences. The General MIDI standard
utilizes all 16 channels available in MIDI. The QuadraSynth Plus is a perfect
General MIDI companion, since its Mix Mode uses 16 channels. Although many
channels are commonly used for specific types of instruments (Example: Channel
1 is usually piano, channel 2 is usually bass, etc.), channel 10 is always used for
drums.
General MIDI also standardizes the placement of sound types in a sound device’s
memory bank. The QuadraSynth Plus’ Preset 4 Bank is designed specifically for
General MIDI, and organizes it sounds according to the General MIDI
specification. This means, when a sequencer sends a MIDI program change
message that is supposed to call up a particular sound, the correct sound on the
QuadraSynth Plus will be called up, even if the composer of the sequence used a
different sound device. The Programs in Preset Bank 4 use the General MIDI