Yahoo Tuning Groups Ultimate Backup tuning Rev 1 of FAQ: what is adaptive tuning?

As always, comments and/or replacement entries are welcome.

=====================================================================

Adaptive tuning (also called dynamic tuning) is the process of modifying
the tuning of pitches as a piece is played, to best suit the intervals
and chords at each moment. Usually the goal it to achieve, or at least
approach, some form of Just Intonation (JI).

There are many types of adaptive tuning:

. Fixed Adaptive Tuning (FAT) vs. Variable Adaptive Tuning (VAT).
See below for an explanation of this distinction.

. Method of making tuning choices: performer vs. computer program.

. Real-time adaptive tuning vs. "leisure" tuning, with the latter
able to make choices based on an entire work, and the former able
to see only the past and present.

. The particular tuning targeted: 5-limit JI, 7-limit JI, etc.

. Whether exact JI intervals are mandated, or whether, for the sake
of reducing the retuning of notes continuously sounding, intervals
may deviate somewhat from exact JI.

. Whether "drift", the tendency of the overall absolute tuning to
change progressively over time, is to be allowed, or is to be
forbidden.

FAT achieves adaptive tuning by making dynamic use of a fixed set of
available pitches, almost always on a keyboard instrument. The number
of possible pitches is usually determined by the number of physical keys
available to the player. This has the advantage of giving the artist
complete control over the adaptive tuning used, at the expense of
limiting to some extent the range of what can be done.

A theoretical method for FAT was first proposed by Nicola Vicentino in
1555. One keyboard manual consists of 19 consecutive fifths tuned to
1/4 comma meantone; the other corrects for flat meantone fifths (and
minor thirds) by being tuned 1/4 syntonic comma (5.38 cents) higher.
For more information, see [Margo's entry].

VAT means that there is a continuous gradation of possible tunings for
a given pitch. VAT can be produced by some acoustic instruments, by the
human voice, and by many electronic instruments. Barbershop singing
makes heavy use of VAT, and to some extent, so do jazz and blues singing
and playing. More recently, there have been experiments with retuning
programs that apply VAT to MIDI files.

The challenges of adaptive tuning are easily illustrated: consider the
sequence C->A->D->G->C, either with bare notes or with the chords Cmaj,
Amin, Dmin, Gmaj, Cmaj. The ideal tunings for the four sequential
intervals are 5:6, 4:3, 4:3, 4:3, but the product of these, corrected
for octave, is 80:81, the famous (or infamous) syntonic comma. One way
to deal with this challenge is to let the absolute tuning "drift" over
time, in this case downward by about 1/5 semitone each time the sequence
is played. Over the course of a reasonably long piece, drift of this
sort can easily amount to a large fraction of an octave, if not more.
There is a school ("Strict JI") which accepts such drift in order never
to compromise simultaneous intervals or retune sounding notes. If drift
is considered unacceptable, however, then difficult choices have to be
made, at least in modifying the tuning of notes which are continuously
sounding, and (optionally) in compromising to some extent the tuning of
intervals.

Real-time adaptive tuning by program is superior to leisure tuning in
that one need not wait for the results: as a piece is played, it is
tuned. However, since chord transitions often involve a several
milliseconds of overlap, not to mention slight arpeggiation of the new
chord, a real-time program can easily become confused and make bad
choices that have to be corrected with painful motion of notes already
sounding. This difficulty is particularly intense when tuning targets
7 or higher limits, in which tuning deviations are much greater than in
5-limit music.

At least one commercial program is available for real-time VAT (see link
below), and at least one list member has dabbled in leisure VAT of MIDI
files. The field of adaptive tuning is still in its infancy, however,
and many refinements have yet to be made. Also, there is a great deal
of controversy regarding what target adaptive tunings (if any) are
suitable, or appropriate, for works of past masters.

For further information:

Commercial real-time adaptive tuning:

http://www.justonic.com/

Experimental leisure adaptive tuning:

http://www.adaptune.com

A real-time, computer controlled FAT piano:

http://tigger.cc.wmich.edu/~code/groven/

[I wrote:]
>>There are many types of adaptive tuning:

[Paul E:]
>It appears here that what you mean is "there are many choices one has
>to make in approaching adaptive tuning", since what follows is not
>actually a list of distinct types of adaptive tuning but rather a
>list of concurrent dichotomies. Calling these "types" could lead to
>the impression that they're items in a list, from which you only need
>to choose one.

Agreed; I will make that change.

[JdL:]
>>There is a school ("Strict JI") which accepts such drift in order
>>never to compromise simultaneous intervals or retune sounding notes

[Paul:]
>I don't believe "Strict JI" refers to this school any more that it
>does to the school which opposes drift but allows retuning of
>sounding notes by a full comma. Strict JI, I believe, simply means
>that all the pitches are selected from a somewhat contiguous region
>of the JI lattice.

OK, I'll remove the term.

JdL

Rev 1 of FAQ: what is adaptive tuning?

🔗John A. deLaubenfels <jdl@adaptune.com>

🔗PERLICH@ACADIAN-ASSET.COM

🔗John A. deLaubenfels <jdl@adaptune.com>