Everything you make has a copyright from the instant it was created, such as music, art, and poetry.
Registration is not required. However, if somebody infringes your work (steal) you'll be limited to standard state law. For a one-time $35 registration fee with the U.S. Copyright Office, you'll have the benefit of federal laws to protect your against infringement.
The $35 registration fee (online submission) is for material that classifies as single application. Examples are one essay, one logo, or one song created by one individual without any co-authorship.
Examples that do not qualify are websites, joint partnership, or song with accompanying cover art. The fee is $55.
The registration fee for a paper-based application is $85.
Copyright works like a time-stamp. Submit a copy to the Copyright Office and get a certificate with a date when received.
If an infringer claims your work as their own: (1) prove the two works are the same and (2) that you have the earlier time stamp.
The original time-stamp only protects what was submitted the first time. Any revisions to the original copyright require a new registration.
A copyright application requires a copy of the best edition of your original work to be deposited with the U.S. Library of Congress.
What is a Copyright?
The owner of a registered work has exclusive rights.
(1) Reproduce the copyrighted work
(2) Prepare derivative works
(3) Distribute copies to the public by sale or other transfer of ownership, or by rental, lease, or lending
(4) Public performance
(5) Public display
(6) Public performance by means of a digital audio transmission (sound recordings)