It defines a standardized group of sounds and the minimum requirements for Gen-eral

MIDI compatible synthesizers or sound modules, so that a specially prepared

sequence or MIDI file that is sent to the instrument via MIDI will play back the cor-rect

sound types, regardless of make and model of the instrument.

MIDI identifies sounds by their program change number. Before the General MIDI

standard was introduced, the same MIDI program change number often addressed

totally different types of sound in any two synthesizers or sound modules from dif-ferent

manufacturers, e.g., a flute type sound in one instrument and a piano type

sound in the other.

With the introduction of General MIDI standard compatible instruments this

changed. These instruments use the same program change numbers for the same

types of instruments.

So, if the person that prepared a sequence or MIDI file wants the melody to be

played by a "piano", he can use a certain program change command embedded into

module. The GM standard does not specify in great detail how that piano should

sound. It is simply assumed that the manufacturer reproduces an acoustic piano

within the capabilities used of the instrument.

General MIDI supports all 16 MIDI channels. Each channel can play a variable

number of voices (thus be polyphonic). Each channel can play a different instru-ment

(or sound, or program). A minimum of 24 fully dynamically allocated voices

are simultaneously available for both melodic and percussion sounds.

which are key-based always use MIDI channel 10 and specific note numbers are re-served

for specific drum sounds.

should respond to. Among these are the MIDI controller events for Volume (Controller 7)

and Pan (controller 10). By using these controllers it is possible to create

a MIDI Mix for a piece of music.

additional standard procedures for selecting alternate drum kits and sound