Any specific format in mind?
One pretty easy format I know of is modules (.mod, .xm, .it, etc). If you can find good samples, you can make some nice music with it.
You'll need a "tracker" to make the music with and a "player" to... yeah, play them. Personally I use the Modplug Player and Tracker, both because they're easy to use (after going through a tutorial). Well, I'm quiting Modules now since I finally have some money to invest in more advanced software, but I consider module tracking a good start <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
Modules used to be a popular format in computer games, but the only games that still have them today are low budget/amateur games I think.
If you want I can give you a few links for info on module tracking, trackers, players and samples, when I get home. One url I can give you now is www.modplug.com