How does music exert such extraordinary effects on our emotions? To what extent does it depend upon our nature (biological rhythms, instinctive reactions to certain sound patterns) and to what extent experience (e.g. conditioned associations, nostalgia)? Particular attention is given to the tension-reduction and optimal uncertainty theories of musical enjoyment. We will also consider whether there is any truth in the claim that listening to music can increase intelligence in the listener (the so-called 'Mozart Effect').