For a mesmeric and beautiful taste of Iranian classical music please try this, featuring the late Faramarz Payvar and his ensemble:
The instruments you are hearing are a santour (a type of zither), a tar (a kind of lute), a kamancheh (somewhat violin-like) and a zarb (drum).
There are six pieces:
Dastgah Shur 10:17
Dastgah Homayoun 7:36
Dastgah Segah 4:47
Zarb solo 4:55
Dastgah Chahargah 4:54
Dastgah Mahour 13:02
The music is true classical music, ancient and full of refinement. Many accounts suggest that its fortunes have not faired too well in modern Iran. Music (except for revolutionary anthems) was banned for ten years following the Iranian Revolution. Faramarz Payvar himself had to withdraw into the private sphere during those years. Pop music has also pushed it to the margins. Hopefully there is still a love for this kind of music there. It is too beautiful to be allowed to die.
In ways not too dissimilar to the ragas of Indian classical music, the music is extemporised on the notes of a modal scale, each piece beginning dreamily before gathering pace and virtuosity. The modal scales are called dastgah (hence the titles above). There are twelve of them, including the Shur, Homayoun, Segah, Chahargah and Mahur (hence the other part of the titles above). 'Modal scale' isn't quite right. There are (as in Western music) seven main notes, but other notes are permitted for the sake of decoration and modulation. Helping guide the flow of melody - and it is essentially a flow melody - are a large set of small melodic cells (several hundred in total) on which the performer draws in a way that's perhaps analogous to the way a jazz musician draw on certain harmonies and chord progressions.
Gorgeous, isn't it?