I still feel there's something not quite right about having instruments on the same level as roles/contributions rather than one level below. To me it seems that if an actor plays a part then their character has the same type of relationship to their role as an actor as an instrument has to a musician's role as an instrumentalist.
Source is a bit weak currently. If it's going to use a fixed vocabularly it needs at least 'other' in addition to 'unknown'. Also a little ill-defined in a way; you might have ripped it off a CD or encoded from FLAC, but where was it before that? I can see this might be useful for organising music collections though. Imalone 04:16, 4 December 2007 (PST)
Categories to be free-form?
Should category's sort attribute and the genere element be free-form or use fixed values? I think at least for the sort attribute a fixed vocabulary could be usefull. To provide a fixed, basic sorting mechanism.