Arabic Tuning

In a list of scales, the exact provenance of which I forget, I
found the following:

Rast Medieval arabic scale t 2s r t 2s r t
Zenkouleh Medieval arabic scale t 2s r 2s t t+r
Rahawi Medieval arabic scale 2s t r 2s r t t
Hhosaini Medieval arabic scale 2s r t 2s r t t
Hhidjazi Medieval arabic scale 2s r t 2s t r

These are based on the intervals

t major tone log(9/8)
s limma log(256/243)
r apotome t-s log(2187/2048)

On the face of it, these are all good Pythagorean scales.
However, intervals of 2s look a bit suspicious. In fact, if you
substitute each 2s for a minor tone and each r for a semitone,
you will see that these are really much more friendly looking
scales in disguise. Rast, in fact, looks suspiciously like a
major, and Hhosaini like a minor.

This approximation rests on the Pythagorean and syntonic commas
being nominally equal, and is very good -- to within 2 cents.
Presumably I wasn't the first to notice this, although I have
heard from two separate sources that Arabic music is based on
Pythagorean tunings, rather than a Pythagorean notation for just
tunings. The following questions therefore arise:

1. How typical are these scales of modern and medieval Arabic
music?

2. Are the scale definitions, which I converted from the
frequency ratios, from a reliable, contemporaneous source?

3. How closely do observed modern tunings conform to JI?

4. Have all Arabic musicians and scholars followed this dogmatic
Pythagorean interpretation?

I would appreciate your answers to these questions. And, while
I'm at it, what exactly does CPS mean?

Graham

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