You wrote a song, now what? 

The first thing you can do is get your song out of your head and on to a medium of some sort. This can mean a simple rough recording on your phone, not only is it good for copyright, but it’s good practice. The medium doesn’t matter, your song just needs to be transferred to a fixed medium.

You’ve accomplished the first step in copyrighting your song! Technically, the moment the song moves from your head to a fixed medium it’s considered copyrighted. The one caveat is that for you to be able to exercise your full rights, like being able to sue someone for copyright infringement, your songs need to be registered with the government, so follow the steps below to copyright your song legally.

The Real Deal – Music Copyrighting

Claims to copyright in published or unpublished musical works can be registered in the Copyright Office.

Published collections of musical works and all the copyrightable elements of a unit of publication can be submitted for registration on one application with a single fee if all the compositions are owned by the same copyright claimant. For details on deposit requirements for published musical works, see Circular 50, Copyright Registration for Musical Compositions.

Unpublished collections of two or more musical works can be submitted for registration on one application with a single fee and a deposit of one complete copy or phonorecord if all the conditions specified in Circular 50 under the heading “Collections of Music” are met.

Follow this link for more information and to Register your song(s) Online:
Copright.gov

Mailing Address for Applications Filed on
Paper and for Hard-copy deposits

Library of Congress
U.S. Copyright Office–PA
101 Independence Avenue, SE
Washington, DC 20559

Online registration
-the preferred way to register basic
claims for literary works; visual arts works; performing arts
works, including motion pictures; sound recordings; and
single serials. Advantages of online filing include:
•a lower filing fee
•fastest processing time
•online status tracking
•secure payment by credit or debit card, electronic check,
or Copyright Office deposit account
•the ability to upload certain categories of deposits directly
as electronic files

Detailed Information Here:
Circular 50 Copyright PDF