A very dense book comparing the modes of Safi-al-din al-Urmawi (1250) to Qutb al-din al-Shirazi (1300). AFAIK, this is the only book in English covering these treatises. There is a lot of analysis which I don't quite understand. It's not really a translation - for that you need to read French, and see Baron d'Erlanger's translations from the 1930's. Owen Wright has gone on to write more books on Arabic and Ottoman and Egyptian and Persian treatises, but he rather assumes that you have this background info in those, so you really have to look at it. I find all of his books difficult to read/understand. He's not writing for a general audience, but for those who already know something about the topic. NB this book only covers modes, there's nothing on rhythm here. Again, for that, see D'Erlanger.