What are the musical origins?

Although there is reference to music, the novel isn't based on any particular genre or musical theme. I don't see music as being any sort of constant theme in the novel though.

No, it's not a constant theme. I am referring to near the end of the novel when it refers to Dunny as being the fifth and it refers to the prima donna, the basso, the tenor and the contralto.

Oddly enough, I have just been re-reading this novel. The last time I read it was like 15 years ago. I do enjoy it. If you give me a little time I'll get back to you tonight.