Music is one of the least competitive courses at Oxford and you'd have almost a 50/50 chance of getting in. It sounds as though you have done your research about the course and it would suit and develop your interests, so I'd say you should definitely apply.
You're already reading around your music interests, so I'd say continue to do that as super- curriculars are more important than any extra- curricular activities. Having said that, it is expected that music students participate in choirs, orchestras and/ or ensembles, so I'd join in musical groups in your school/ college. Good luck!