Yahoo Tuning Groups Ultimate Backup tuning MIDI engine spec, FTS, lists rock

Howdy, all-

Just dropping by to post the spec for the 'root control'
program Robert Walker and I were discussing here a few
weeks ago. I've been milling over this since 1996, when
Denny Genovese and I were discussing it. Finally, I have
in writing a reasonably-specific idea of what I want, and
I thought I'd share it with y'all.

The good news is that the next version of Robert's Fractal
Tune Smithy software, together with your favorite sequencer,
will support almost all the behavior described in this
spec... in addition to a bunch of cool stuff Robert's
cooked up, inspired by CPS's. But I don't want to spoil
all the surprises... Let's just say that if everything works
out, for the first time ever you won't have to pay $$$ for
a Kurzweil synth to do this. Look out, Wendy Carlos!

I'm also going to post about this on the Tuning List. I'm
un-subscribing from this list as soon as this post goes
through, so please respond over there. Or, send mail
directly -- carl_lumma.org ... Just swap the _ for an @.

Cheers!

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Xenharmonic Moving Windows 26 August, 2001
MIDI engine spec

Introduction:

This document describes a procedure for applying tunings with more than
twelve pitches per octave to MIDI instruments. In particular, it aims
to present these tunings twelve pitches at a time, in order to
facilitate their use by composers and instrumentalists having access to
and experience with the tools of traditional 12-note music... such as
notation and ear training, keyboards and fingering, staff paper and
sight-reading, and so on.

The procedure defines two different types of MIDI channels -- "control"
channels and "window" channels. Window channels make up the musician's
12-note view of the larger virtual tuning, while control channels allow
him to move this window around in the virtual tuning. The procedure is
described in the context of a software implementation for Microsoft
Windows.

The software uses both Pitch bend and MTS Sysex for tuning MIDI
instruments. Pitch bend is supported by nearly all MIDI instruments,
but requires twelve window channels on a single instrument for mono-
timbral performance.^1 MTS Sysex is supported by a smaller variety of
MIDI instruments, but requires only a single window channel for mono-
timbral performance. In either case, multitimbral performance may be
achieved by using more than one MIDI instrument.^2

This document distinguishes between pitches and intervals. Pitches are
written as octave-equivalent ratios with a slash, relative to a given
reference frequency. Intervals are written as octave-equivalent ratios
with a colon, measured from a given reference pitch. So "5/4" refers to
a particular frequency, while "5:4" refers to a distance from a given
pitch... "25/16 is found a 5:4 above 5/4".

Output:

(1) MIDI stream.
The software should present itself to Windows as a MIDI device,
taking MIDI-in from other Windows MIDI devices and sending
Windows-friendly MIDI-out in real time. The total turn-around
time ("latency") should be less than 10 ms.

(2) Save-to-file. (.mid)
The software has a MIDI stream buffer, which may be dumped to a
General MIDI file using standard MFC "save-as" dialogs.

(3) Save-to-file. (.txt)
The software generates a standard text file from the MIDI
buffer, showing the final tuning of each event on the window
channel(s) as cents deviation from 12-tET, on a tick-by-tick
basis.

(4) Save-to-file. (.scl)
The window intervals may saved as a Scala file.

Input:

(1) Tuning reference. (1-128)
The given MIDI note and its default pitch are taken as a
reference point.

(2) Window intervals. (.scl)
A size-ordered list of twelve octave-equivalent intervals, given
in cents 1 -> 1199 and/or proper fractions 99:98 -> 99:50.
These intervals and their octave equivalents are applied to the
reference pitch in (1) and mapped to consecutive MIDI notes to
create the initial scale for the window channel(s). The window
intervals may be populated from standard Scala files (.scl) when
they define exactly 12 notes (else they should return an error).

(3) Retune type. (Pitch bend/MTS)
For each Windows MIDI instrument, the user selects either Pitch
bend or MTS.

(4) MIDI channel setup.
The software displays two empty sequencer-style track sheets,
one for window channels and one for control channels. The user
populates these with MIDI channels from the devices defined in
(3). A given MIDI channel can only appear in one sheet. For
pitch-bend devices, twelve channels at a time are acquired by
the window channel sheet, where a bracket displays them as a
group and gangs their settings together.

(5) MIDI channel settings.
The window-channels sheet contains the following settings:
mute, volume, pan, patch. They function as they would in a
standard MIDI sequencer, and default to: off, 63, 63, and
patch 001, respectively.

The control-channels sheet contains the following settings:
mute, "window channel #", and "control type", which default to:
on, "none", and "none", respectively.

When mute for a control channel is switched off, events sent on
the channel are copied into the channel specified in its "window
channel #" field, immediately after having the control effect
specified in its "control type" field. A "window channel #"
must be specified to enable the mute field.

The "control type" field has the following possible values:
"none", "diamond", "diamondrel", "cross", and "crossfree".

If "none", events on the control channel do nothing to the
window pitches.

If "diamond", the choice of a note from the control channel is
the choice of a position in the original list of window
intervals. The list is rotated to this position and applied to
the reference pitch in (1) to generate new window pitches.^3

If "diamondrel", the choice of a note from the control channel
is the choice of a position in the current list of window
intervals. The list is rotated to this position and applied to
the reference pitch in (1) to generate new window pitches.^4

If "cross", the choice of a note from the control set is the
choice of a pitch -- the pitch found on that note in the initial
window mapping created in (2). This pitch is placed into (1),
and the window pitches are rebuilt accordingly.^5

If "crossfree", things happen as in "cross", except the new
reference pitch for (1) is taken from the current -- as opposed
to the initial -- window mapping.^6

(6) Retune sounding notes? (Yes/No)
When =Yes, tuning changes are applied to notes only at note-on.
Implementation must support the issue of multiple tuning changes
while a note is sounding, and apply only the last (most recent)
tuning when the note finally gets a new note-on.^7

Final Thoughts:

It is natural to imagine using this software with an organ, where the
pedal is assigned to a control channel... with score entry software,
where a particular staff may be assigned to a control channel... We
suggest supporting a maximum of two simultaneous control channels; up to
one each from the "cros_" and "diam_" types.

The author would like to recognize Denny Genovese's contribution to the
ideas presented here, and note that a similar strategy has been used by
Wendy Carlos and was implemented on Kurzweil K2000 series MIDI equipment
at her request.

This document was inspired by a discussion with Robert Walker on the
crazy_music mailing list (http://groups.yahoo.com/), and a version of
the procedure described here is implemented in his Fractal Tune Smithy
software (http://go.to/tunesmithy/).

Footnotes:

^1 Sequential window events are sent to the "least busy" of these
channels.

^2 Or by using a single multitimbral instrument with MTS, or pitch
bend when at least 24 channels are available.

^3 The total tuning available to the musician with a single "diamond"
control channel is the Partchian tonality diamond of the original window
intervals. The reference note in (1) will always be the diamond's 1/1.

^4 This variant gives access to the same total tuning as "diamond",
but offers a different way to think about the roots -- they are given
relative to the window set currently in use, rather than to the original
window set.

^5 This option confines the total tuning to the Cartesian cross
product of the window intervals, with a maximum of 78 pitches (because
the Cartesian cross product has a plane of mirror symmetry, the maximum
number of pitches needed to play in every key of a scale with n notes is
not n^2 but n(n+1)/2 -- the classic formula for the sum of natural
numbers up to n).

^6 The result is similar to that of "cross", except the total tuning
is unbounded, and the pitch at the chosen note will never change as a
result of the choice.

^7 When the window intervals are in just intonation, =No facilitates
"crunchy" (Keenan Pepper's term) suspended chords.

-=Carl Lumma
Berkeley, California

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MIDI engine spec, FTS, lists rock

🔗Carl Lumma <carl@...>

🔗Robert Walker <robertwalker@...>