The way in which copyright protection is secured is frequently misunderstood.
Copyright is secured automatically when a work is created.
A work is "created" when it is fixed in a tangible form for the first time.
For example, a song (the "work") can be fixed in sheet music, phonograph disks or both. No publication, registration or other action in the Copyright Office is required to secure copyright.
There are, however, definite advantages to registration, including the ability to sue for infringement.