For the purposes of copyrighting your work you should know what it means when someone says musical composition versus sound recording.
According to the United States Copyright Office at http://www.copyright.gov/register/pa-sr.html
“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.”
Therefore, as stated on the website, the copyright in a sound recording is not the same as, or a substitute for, copyright in the underlying musical composition.
Still confused? Most people are, so let’s try to some different wording that hopefully will help.
According to section 101 of the U.S. Copyright Act, sound recordings are “works that result from the fixation of a series of musical, spoken, or other sounds, but not including the sounds accompanying a motion picture or other audiovisual work, regardless of the nature of the material objects, such as disks, tapes, or other phonorecords, in which they are embodied.”
The song itself is an original work of authorship consisting of music (melody, harmony, rhythm) often combined with lyrics, another way to think of this is when you write the lyrics of the song, you write down the words, and have a melody in mind.