Add a copyright notice to the CD. Proper notice includes three things: the phonorecord copyright symbol (the letter P in a circle), the year that the CD was first published and the name of the copyright owner. The notice must be "permanently legible to an ordinary user." Printing the notice visibly on the CD should be sufficient.
Determine whether you need to register the underlying musical compositions. Registering a specific recording of a song is not the same thing as registering the "musical composition" itself (that is, the music and lyrics). If the music was composed by the same person or persons who performed it, you can register both the recording and the underlying composition at the same time. If not, the composer should probably register his composition separately. (You can still register the recording even if the composer has not registered his work.)
Print and fill out form SR. If you are registering the musical composition as well as the CD you should still use form SR, but include information about the author(s) of the musical composition and the sound recording. (They are the same person, but you fill out the information separately.) If the CD is a compilation, be sure to identify the original recordings in space 6 of the form. If the form is confusing, you may want to seek help from a qualified attorney or an online legal document service.
Collect the deposit and payment. The "deposit" is a copy of the CD if it has not yet been published, or two copies if it has been published. The copies will be deposited with the Library of Congress. Also prepare a check for the appropriate filing fee.
Send your form, deposit and payment to the Copyright Office. The office will take several months to process it. Once it is finished, it will send you a certificate of registration.