Appendix B: MIDI Supplement
170 QS6.1 Reference Manual
SYSTEM COMMON MESSAGES
Intended for all units in a system, some of these MIDI messages are:
Song Position Pointer.
This indicates how many ÒMIDI beatsÓ (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 ÒexclusiveÓ
because different manufacturers send and receive data over MIDI which is intended
only for that manufacturerÕs equipment.
Example:
Sending a QS6.1 message to an
Alesis DMPro Drum Module wonÕt do anything, but the message will be understood
by another QS6.1. 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 theyÕve 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 a
Stop command will re-start units from where they were when they stopped.
G
ENERAL
MIDI
General MIDI (GM) 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 GM standard utilizes all 16
channels available in MIDI. The QS6.1 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 deviceÕs
memory bank. The QS6.1Õs GenMIDI Bank is designed specifically for General MIDI,
and organizes its sounds according to the GM specification. This means that when a
sequencer sends a MIDI program change message that is supposed to call up a
particular sound, the correct sound will be there on the QS6.1, even if the composer
of the sequence used a different sound device. The Programs in the GenMIDI Bank
use the standard General MIDI names, which is handy because many commercially-
available GM sequences have the names of the instruments used in the songs stored
with the track data.