Or you could start with a more personal approach:

• something you're interested in
• something you've always wondered about but have little knowledge of
• something that is particularly controversial or currently topical
• something your professor mentioned in class

• something about which you know nothing, but would like to pursue

Your subject should be an intellectually challenging question or issue rather than just being "about" a composer or a work.

Example:

not "The Music of Aaron Copland,"

but "How Did the Music of a Nice Jewish Boy from Brooklyn Come to Personify the American West?"