31-tET vs. 24-tET for Arabic (and Persian?) scales?

[Paul Erlich, TD 547]:
>If we need to choose a single tuning for this "revival", I'd like to
>suggest 31-tET.
...
>open the floodgates for future possibilities
>involving 7-11-limit harmonies, Arabian scales, microtonal effects,
>etc. etc.

Hi Paul,

I seem to remember reading in the Journal of Ethnomusicology that many
Egyptian musicians now use 24-tET instruments for playing Arabic music
and I have also read that Colonel Vaziri and some of his musical
followers were/are proponents of 24-tET in Persian music and I would
sincerely like to know your views on the advantages and disadvantages of
31-tET vs. 24-tET in this context.

Also, I know you mentioned Arabian rather than Persian scales in your
post, but if you've given some thought to Persian scales in 31-tET too,
what subset of 31-tET would you use for the 17-tone Persian tar/sehtar
tuning (i.e. C Db Dp D Eb Ep E F F> Gp G Ab Ap A Bb Bp B C)?

Thanks,
Christopher

>I seem to remember reading in the Journal of Ethnomusicology that many
>Egyptian musicians now use 24-tET instruments for playing Arabic music
>and I have also read that Colonel Vaziri and some of his musical
>followers were/are proponents of 24-tET in Persian music and I would
>sincerely like to know your views on the advantages and disadvantages of
>31-tET vs. 24-tET in this context.

Probably the only difference noticeable to most people would be the wide
semitones in 31-tET. Basically, for any of the 7-tone scales used in Arabic
music, take the step sizes in 24-tET (which will range from 2 to 6) and add
1 to each of them; then you'll have the step sizes for the 31-tET version of
the scale. So, for example, the very common scale C Dp Eb F G Ap Bb C, which
has step sizes 3 3 4 4 3 3 4 in 24-tET, would have step sizes 4 4 5 5 4 4 5
in 31-tET. A comparison of cents values:

24-tET 31-tET
0 0
150 154.8
300 310.8
500 503.2
700 696.8
850 851.6
1000 1006.4
1200 1200

>Also, I know you mentioned Arabian rather than Persian scales in your
>post, but if you've given some thought to Persian scales in 31-tET too,
>what subset of 31-tET would you use for the 17-tone Persian tar/sehtar
>tuning (i.e. C Db Dp D Eb Ep E F F> Gp G Ab Ap A Bb Bp B C)?

Since the typical maqam or dastgah takes 1 note of each letter-name, and
since this is 0 2 3 4 6 7 8 10 11 13 14 16 17 18 20 21 22 24 in 24-tET, it
would be 0 3 4 5 8 9 10 13 14 17 18 21 22 23 26 27 28 31 in 31-tET.