> I'm a newcomer here.  Has the issue of non-12 tone music come up here 
> before?

Yes, I've posted two or three fairly detailed proposals over the years,
covering both playback and printing.


> A lot of middle eastern (Turkish, Arabic, Persian, etc...) music is 
> based on a quarter-tone (24 division) system; or in the case of some
> Turkish music up to 48 (or even more) divisions of the octave.

No they aren't.  Quarter-tones are sometimes used in modern texts
(particularly Arabic ones) as an approximation to the real thing,
but the underlying model of Middle Eastern and Indian-subcontinent
music is much more sophisticated.

What all these genres use is the idea of a mode created by selection
from a large microtonal pitch set.  In Indian music this is the 22
"shrutis" (whose pitches are not necessarily equally tempered and
probably vary between regions and idioms); in Turkish or Iranian
music the basic unit is the Pythagorean comma (with a secondary
measurement scheme derived from it forming a namelessly implicit
24-note non-equally-tempered pitch set which functions like the
shrutis and is represented by the fretting of the tanbur).  From
this you derive the modes - ragas, makams, dastgahs - by selecting
from that large set:

  1. a rising pitch set
  2. a falling pitch set
  3. a few optional accidentals
  4. a bunch of standard melodic cadences

The rising and falling sets are not usually very different and don't
have more than 7 notes, the accidentals tend to be used sparingly,
and the cadences can't be represented in a key signature.  So what
happens is that people reduce each mode, for purposes of printing,
to one key signature (the rising scale) and indicate the variations
used for falling passages or cadences by accidentals.  That system
makes a suitable target for an ABC representation.  The elements that
need to be incorporated are:

1. the underlying pitch-measurement scheme (shrutis, commas, cents,
   harmonic ratios, rational fractions of a tone and probably others
   I haven't thought of)
2. selections from that to (reusably) define 7-note modes, mapping
   these onto ABC note names (Indian music uses modes with fewer
   notes, but these are considered as derived from 7-note modes)
3. a means of representing accidentals in ABC source
4. a library of graphical signs to represent the microtones in either
   the key signature or in accidentals within the tune body when
   creating staff notation (there are only a few of these, see any
   text on Middle Eastern music).

What that would give you is a representational scheme which extends
ABC in exactly the right way to match the model of microtonal-modal
music already in use by its practitioners.  A scheme which requires
people to use MIDI and fractions is so alien to the way anybody
actually thinks about this stuff that it would be utterly unusable.
You MUST have a way of defining named modes so you can refer to notes
by single letters, the way you find them named in Indian music texts.

Karl Signell's _Makam: Modal Practice in Turkish Art Music_ is a good
place to start in identifying the issues (he makes a clear distinction
what what happens notationally and what actually goes on in practice,
something Turkish sources tend not to do - there are situations where
you want to notate theoretical rather than actual intonation, just as
there are in Western diatonic music).


-----------------------------------------------------------------------------
Jack Campin: 11 Third Street, Newtongrange, Midlothian EH22 4PU; 0131 6604760
<http://www.purr.demon.co.uk/jack>     *     food intolerance data & recipes,
Mac logic fonts, Scots traditional music files, and my CD-ROM "Embro, Embro".
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