As far as I'm aware (I'm actually quite sure about this), the Seven Ahruf were revealed according to the seven dialects of the Quraysh tribe. 10 riwayat(transmissions) have reached us. The should be distinguished from the original 7 Ahruf, because some of the differences are in transmission.
Even among these 10, there are differences among the students who transmitted these Qira'at.
I can recite Surah Maryam in Duri, and Surah A'la in another style (can't remember the name, but they read 'ee' as 'ay' (with amalah) and pause when a 'laam' is followed by a 'hamza').
