I think I've picked the wrong course, what should I do?

I'm starting university at Brighton for the first time on the 25th of September to study a BA in Animation. At first I was optimistic, but as the time to moving in and starting draws near I'm really beginning to think that it's not what I want to do. I don't have an issue with moving away or going to university (I'm rather looking forward to moving out and getting my foot into the world), it's the course which is putting me off.

I think what I really want to study is Music Production. I desperately wanted to do Music Production at A Level, but in the end I didn't and I regretted not going to college for it through my entire time at Sixth form. So much so that I nearly dropped out at the end of year 12 to enrol in the college, I only didn't go through with it because the college told me it would be in my best interest to finish my A Levels instead. And now I think that desire is resurfacing, I don't want to make the same mistake and go through the hell that was those 2 years of sixth form again.

The thing is, I've already got a confirmed place at the university and in halls accommodation. They also don't offer Music Production as a course either. I don't know what I should do. I don't know if it's the best idea that I should apply elsewhere through clearing now, if I should try the first few weeks of Animation and then apply through clearing if I still feel the same way, or should I try it for the first term and if I decide it's still not what I want; drop out and apply for next year? I'm really at a loose end here.

I realise that it's not the end of the world. My brother dropped out of university twice before he found the course that was right for him, which also happened to be music. I just REALLY don't want to spend another year out of education after having a pretty bad gap year. I'm so scared of making the wrong decision.