So I dont know.....most alt/indie we would expect to be vaguely leftie/green/anarcho
most pop we would expect to be bland and whatever the papers said
most rock we would expect to be left or right, but a bit more extreme about it

but what about the classical musos? Apart from wagner being portrayed very successfully as a punk in amadeus, and many composers having very tragic lives, is there any generalisation that could be applied to them politically?