Re MIDI Tuning Spec

In Digest 1194 John Loffink writes:

>A MIDI byte takes 320 microseconds to transmit. Let's say you have
>a fairly dense arrangement with 20 notes on 10 MIDI channels sounding
>as you modulate to another tonic. It takes, not counting the actual
>note ons, 320 us per byte x 12 bytes per message x 20 sysex messages =
>76.8 milliseconds to send the updated tunings to the various
>instruments. This is clearly not adequate.

The 20 sounding notes receive no sysex. Only when a note is struck does
it need a prefixed sysex real-time pitch-change message. The combo is
essentially a 15-byte note-on including high-precision frequency data.
Bandwidth really isn't the issue here, unless you think a (320us * 15
bytes = 4.8ms) delay on a note is a problem. (And if you do, you should
be aware that that degree of slop is more or less average for MIDI
equipment.)

>If I want sustaining notes to hold their current tuning while sounding
>new notes in a new scale, what are my options? If it's back to the
>individual sysex messages per note, I'll need some MIDI Draino to unclog
>the limited bandwidth.

You strike a note on your keyboard; a MIDI note-on goes out to some
computer host. Software gets the note-on, figures out what frequency
you want, and prefixes a 12-byte frequency message to the note-on,
passing the combo on to audio hardware. (If that particular MIDI note
number is already sounding on the channel requested, software changes
the struck note number. Note number is independent of pitch in the
Tuning Spec. The only limit is the MIDI limit of 128 notes per
channel.) Sustaining notes aren't affected at all.

So yes, it is back to individual sysex messages per note. A pain in the
neck to type into a sequencer, for sure. It would be much nicer if we could
compel every manufacturer to include 64 or 255 tuning tables, all accessible
and switchable the same way. We can't, so instead we wrote a (mostly
ignored and obsolescent) standard so that at least the sysex codes might be
the same for different instruments.

Still, to use the standard practically for dynamic JI you need some
software pre-processing tool (like Justonic). But the problem shouldn't
be MIDI bandwidth.

Am I being clear, or have I missed something?


SMTPOriginator: tuning@eartha.mills.edu
From: Mark Nowitzky
Subject: Ben Denckla's Masters Thesis
PostedDate: 01-10-97 12:17:27
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