look into creative commons.
http://creativecommons.org/
as for copyright law in general, look here:
http://www.case.edu/affil/sce/authorship/syllabus.html
alot depends on the type of music you are doing and the kind of control you want to have over it. if you are releasing materials through a website a creative commons copyright might be more reasonable than a straight one--if you see music recorded as commecial for live performances and by using your webstie are basically conceding that you are not doing the recordings for cash as the objective, then it makes sense.
if you do not stipulate the kind of copyright you want, you will default to existing copyright law.
for the kind of music i do, straight copyright is useless because we do not use scores. we could score it ex post, but the notation would still not describe the kind of sound, so it is a waste of time. we would like to have some control over how our stuff is used, but more at the level of knowing about it than at the level of putting a record label in a position to sue someone for not paying them for your music.