Even though I'm doing HSC now, in prelim we did Jazz, music for small ensembles and popular music. Basically we covered each topic for a term each. Although none of our assessment taks had anything to do with Jazz. But in music, I don't think it really matters so much how well you go through each topic, because in the end it becomes a little irrelevant (like the history of the sort of music) what you you do in each. Basically you do your musicology, performance or composition relating to one of the topics, so you just need a basic outline of what the topic involves and if you're having trouble with that, then doing music probably isn't your best choice. But then when you do aural tasks, try and take note of things which are very specific to a certain style, so then when you hear it in an aural exam you can get some brownie points.