" It's often impossible to know precisely where the individual musicians are in the beat (although they do), as they constantly engage in micro-shifts of their rhythms in response to each other and the dancers"
I think that the above statement is true of any group of good, improvising musicians, when they "get in the groove".
I've been lucky enough to play with some very good Senegalese musicians, and it is exactly like that. You start by playing a conventional pattern, then with tiny variations in timing and emphasis- too small to notate in a musical score- the whole ensemble locks into a groove. Then somebody makes a change, often looking around at the other players with a grin, and the others will smile and nod and pick up the new groove.
But I've seen the same thing in a Trad Jazz band and with Bluegrass musicians!
I rejoice to see that Al Jazeera are promoting music as a model of social solidarity though. There is a lot of anti music feeling amongst the Puritanical branches of Islam, and it seems to me to be a threat to a very rich Islamic musical culture.
Cheers
Dave