SEQUENCING CLASSICAL MIDI TUTORIAL
4. GM/GS
If you choose to keep your sequence's to some sort of GM/GS
specification then you should be made aware of certain advantages and disadvantages.
Yamaha's GM (General Midi) and Roland's GS (General
Standard) were born to enable a certain amount of compatibility
between different sequence's and instruments. In its most basic form it
enables the patches set up from one system to be adhered to by another.
For example, if one sets a strings patch 48 on one GM/GS
instrument then that same patch 48 will be recognised by all
other GM/GS instruments as strings. In principal
this should make a sequence sound almost identical on whatever GM/GS
instrument is reading it. However, because each manufacturer samples their
patches differently a true reproduction is not always possible. But if a
sequence is programmed using, for example, a Roland SC55 then
that sequence will sound identical on all other SC55's.
One drawback of the use of GM/GS is its insistence of the
maximum polyphony of only 24 notes, or more accurately, partials.
Polyphony is the number of notes, or partials, that can be played at the
same time. A polyphony of 24 notes may sound a lot to most people but when
you are considering sequencing classical scores, especially scores written
for full symphony orchestra's, then this limitation can cause problems.
It doesn't help either when you find some patches you need to use are made
up of more than one partial so thereby reducing your working polyphony even
further. There are, however, instruments that go well beyond the 24 note
polyphony but for maximum compatibility you are best keeping to the limitation.
There are a few solutions to 'cheating' the limited polyphony and they will
be discussed later on in this chapter. |
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