tuning tables in GM

Hi, Murat!

>Since GM instruments/cards accept tuning on different channels...
>Is there a possibility to have different tunings on different MIDI
>channels? i.e. a Turkish tuning on the first and Thai in the second?

(For those not familiar with the wonderfully maddening world of MIDI, GM is a
standard called General MIDI. It consists basically of a set of similar
sounds that can be called up by the same set of MIDI patch numbers, plus
misc. other commands designed to allow sound modules from different
manufacturers to play back a MIDI file more-or-less predictably.)

I believe the answer is a qualified yes. It most likely varies from "no" to
"yes, different tuning on each of the 16 channels" from manufacturer to
manufacturer, and from instrument model to instrument model within a
manufacturer's line. Whether you could find some usable standard for
distibution of tuned GM files is a question for a more learned authority.

Here's what I know for certain. I have a Korg O5R/W, which is GM compatible
and is mainly marketed as a PC peripheral, street price, new, about $600.00
US.

1) Its tuning table has 1-cent resolution which is not great but alot better
than nothing
2) It has a handful of common historical and ethnic tuning emulations in ROM
3) In addition it allows *one* user-defined tuning in RAM (uses SysEx to
save/load user tunings to/from a computer)
4) It allows the use of only two different tunings at once, any channel can
be assigned to either tuning, and any individual channel can switch to the
other tuning flawlessly, on the fly, with no interuption of sound :-) by use
of Controller #4. In fact, switching tunings on a channel during a sustained
note causes its pitch to change instantly, which I find a little
inconvenient. I wish it would only apply the changed tuning to subsequently
triggered notes. That would allow real-time tunings with 24 pitches
(provided that at least 12 of those were already in a single ROM tuning).
But Alas!
5) The factory tunings always put "A" at 0 cents, so that "C" is always
tuned away from the 12t-ET standard. I could see that if the tables ran from
A-G#, but they don't - they run from C-B; that can make it clumsy to use the
ROM tunings as a starting place for a user scale, or to combine user and
factory tunings.

It *might* be possible to take advantage of a wider pallete of tunings by
sending SysEx data from the MIDI file during playback. But I suspect that
this would cause a delay in the processing of the sounds during the dump. My
uncertainty stems from the fact that my sequencer doesn't support SysEx in
tracks, only in a separate screen which cannot be accessed during playback.
Still, I doubt that it would be a reliable technique for music production.

Good luck!

David J. Finnamore
Just tune it!

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