Congratulations, you've just composed some music! You are a poor college student needing to copy music from the library or you just want to try a work before you buy. You are a faculty member who wants to use music in your classes and that whole Fair Use is gibberish. Copyright confuses EVERYONE! This page lists a few basic facts and several links to help you figure out if you're breaking the law. Copyright is very serious. If caught, composers and their representatives can take legal action that will make your tuition payments seem like Tooth Fairy money. Respect your fellow musicians. Don't abuse copyright.
1) Compositions published in the US before 1925 are Public Domain (PD). That means you can copy until you run out of paper and toner. These works are represented in IMSLP which is a great resource for printing music scores. Sound recordings fall under a different rule and are probably under copyright.
2) Compositions published in the US after 1978 are protected for 70 years AFTER the composer's death. They are protected for 95 years if published by or copyright is owned by a corporation. Basically if something was written after 1978, it's almost definitely under Copyright protection unless the composer released the rights to a creative commons license. You need to be very careful with post-1978 music, especially in a public setting.
3) Composers may terminate copyright contracts 35 years after the date of transfer or granting of the copyright. In case you got a bum deal with the publisher or record label.
4) There are particular rules to "cover"ing a music work. Make sure you're familiar with them before choosing to perform somebody else's work, especially if it involves a visual component like movie soundtracks, video games, etc.
5) Be very careful of Public Performance rights. Make sure you have acquired the appropriate licenses from licensing agencies before performing a copyrighted work or showing a movie of a copyrighted work in public.
