XG programChange -- Was: Re: [fluid-dev] invalid instrument/drum selection

[jimmy]

Hi Josh,

About XG (and GS) program changes, and how missing instruments might be 
handled,  Here are some comments and observations I found around the web.  I 
think missing drum-kits should be handled similarly.


>>>>>
   archive.cs.uu.nl/pub/MIDI/DOC/xg.txt

Both specs also operate a scheme of tone 'fallback', whereby if a 
variation tone is not present at a given bank program number, then the 
synth will fall back to using the corresponding GM tone. (the GS spec 
does this in a cascading fashion, i.e. falling back to the next lowest 
variation tone of the same program number....this can be confusing).

The advantage of the fallback scheme is that if a song uses variation 
tones and is played on a synth of lesser specification (or purely GM 
specification) then the voicing will still be acceptable (although not ideal).
<<<<<


>>>>>
   
cybermidi.powweb.com/faq/content/3/22/en/what_s-the-difference-between-gm-gs-and-xg.html

Although the XG format defines an extensive range of parameters and allows 
exceptionally fine musical control, not all XG devices need to conform to the 
full XG specification. The XG format allows features and capabilities to be 
"scaled" according to price and target applications. When music data is played 
on a scaled-down XG device, playback is adapted to the capabilities of the 
device used. If, for example, a specified voice is not available for a certain 
part, that part will be played using a similar basic voice. On the other end of 
the scale, models equipped with a graphic equalizer can be automatically set to 
play hard rock pieces or classic compositions with appropriate overall EQ.
<<<<<


>>>>>
   www.somascape.org/midi/help/intro.html

The voices in the extra banks align with those in the standard GM bank, thus 
providing variants on the standard voices. This means that a MIDI file composed 
for use with a GS or XG device will sound okay when played using a standard GM 
device (because a GM device will ignore any Bank Select messages and just 
respond to the Program Change messages).
<<<<<


Jimmy