Copyright Registration Sound Recordings Works
First, let's pinpoint what falls into the sound recordings category. Here's what the US Copyright Office has to say:
"Sound recordings are 'works that result from the fixation of a series of musical, spoken, or other sounds, but not including the sounds accompanying a motion picture or other audiovisual work.' Common examples include recordings of music, drama, or lectures."
Here are some books about copyrights:
The Copyright Handbook
How to Register Your Own Copyright
Now to file an application:
The application is fairly simple & the cost is $45 per application.
Despite what others state, a "poor man's" copyright is NOT the same as registering it. Here's what the US Copyright Office has to say:
"The practice of sending a copy of your own work to yourself is sometimes called a 'poor man’s copyright.' There is no provision in the copyright law regarding any such type of protection, and it is not a substitute for registration."
Lastly, here are two great resources:
NOLO's Copyright Resource Center
NOLO's Creative Arts & Music Resource Center