As stated on the RetroGamingRoundup 7ish hour podcasts, the C64 was really overdesigned for what it needed to be, and the kick ass SID chip afforded programmers to produce some of the best chiptune music of all time. Of course, there are many examples of C64 games with poorly composed/bad music, but that's the fault of the creator, not the C64.

Some tracks worth taking a look at include the C64 version of R-Type, the title theme of Robocop 3, and pretty much any track from the Great Giana Sisters which is still the best Mario clone ever made.