 Al-Farabi (872–950) is a notable representative of the Aristotelian current in medieval Islamic philosophy of music (see Shehadi 1995: chapter 3). Farabi rejects the harmony of the spheres. Rather than speculating about music’s origin in the structure of the cosmos, he attempts to understand it as a human phenomenon, suggesting that vocal music may have developed out of necessities such as the expression of pleasant and unpleasant states. Farabi also distinguishes three types of melody, according to the effect it produces in the listener. Some melodies are pleasing to the ear, others evoke images, and yet others express psychological states. It is possible for a melody to do more than one of these things, and in fact Farabi holds that the best melodies tend to have all three such effects.