All the arts can be seen as a manifestation of one and the same impulse. The drive to the arts must surely have had a biological origin. But why do these types of behaviour exist? Why should Beethoven choose the massive labour of composition rather than eating, drinking, a family life? Maybe there was the desire to create a `ktema es aei` (a possession for ever), in the awareness of death to survive somehow, but this does not indicate why his activity took this specifically artistic form.
The basic biological drive, impelling composers to compose, artists to paint, poets to write and even scientists to do their science is towards exploration of the perceived world (the outer world and the inner world) and the attempt to replicate it in some durable form. In a sense artists and musicians are engaged in exploration of the properties of the eye and exploration of the properties of the ear.