Visit the U.S. Copyright Office online. You can register your song over the Internet and upload it for deposit in the Library of Congress. You can register by mail as well, but the filing fees are higher.
Instead of requiring a different form for stories, screenplays, songs and music, the U.S. Copyright Office has initiated the use of Form CO. This form can only be used to register one song, not a group of songs. If you have more than one song, you will need to use Form SR.
On the home page of the U.S. Copyright Office, click on "Electronic Copyright Office" under "How to Register a Work." Consider reading the recommended material before you attempt to register your work. Links to the recommended reading appear at the top of the registration page. This material will answer many questions you might have about copyright registration.
Register your song or songs. You can register several songs together if the copyright owner is the same for all of them. The benefit of registering a group of songs together is the cost--the same filing fee applies. For songwriters, you should register your songs by album. Check www.copyright.gov for current fees.
Upload mandatory copies of your work for deposit and check your e-mail for copyright registration verification. If there is ever an infringement suit, the U.S. Copyright Office will give you verification of the date you registered.