Well, actually, in the case of the United States and I think the European Union as well your work is in fact automatically copyrighted from conception. That doesn't mean it comes with proof of ownership, though. ;) It's not worth worrying about if composition is not currently your livelihood. What you should be worried about at this point is developing the skills necessary for a career in composing so that in the future, you will have compositions worth stealing. It's not my intention to diminish your work, it's just that I'm only too familiar with the paranoia associated with distributing one's material. Then I came to look at compositions more as a reflection of your skill as a composer and less as fluke accomplishments that need to be protected at all costs. Even if a composition of yours is stolen - I'm not saying it's not horrible - write another one. It only becomes a "real" issue if it being stolen deprives you of income. As for your compositions being repeatedly stolen - it's possible, but so is being struck by lightning, which is something most of us will never come close to experiencing - it is not something you should count on.