For copyright purposes, there is a difference between MUSICAL COMPOSITIONS and SOUND RECORDINGS.
A Musical Composition consists of music, including any accompanying words, and is normally registered as a work of performing arts. The author of a musical composition is generally the composer and the lyricist, if any. A musical composition may be in the form of a notated copy (for example, sheet music) or in the form of a phonorecord (for example, cassette tape, LP, or CD).
A Sound Recording results from the fixation of a series of musical, spoken, or other sounds. The author of a sound recording is the performer(s) whose performance is fixed, or the record producer who processes the sounds and fixes them in the final recording, or both.
Copyright in a sound recording is not the same as, or a substitute for, copyright in the underlying musical composition.
Although they are separate works, a musical composition and a sound recording may be registered together on a single application if ownership of the copyrights in both is exactly the same. To register a single claim in both works, complete Form SR. Give information about the author(s) of both the musical composition and the sound recording.