Current Y11 are doing old spec music, so might be best to post separately about 1-9 Music for the attention of parents of current y10s, who will be the first to do the new spec.
The old spec that DS has just done has 3 elements - performing (solo and in an ensemble); composing (2 pieces) and a 'listening and appraising' exam (done today) in which they have to listen to and answer questions about a number of set pieces, and write a short essay about one of them.
DS has loved it and wants to carry on to A level. Having a decent level of instrumental ability + some knowledge of music theory makes it easier, and if they already play in some kind of ensemble that can help for the performing (as it can be easier to play really well in an ensemble you play in often, rather than one put together just for the exam)