What qualifies as a musical work?
A musical work is any musical composition. This is not an actual recording of something (that’s known as a “sound recording”); rather, it is the created and written music (song composition, lyrics, etc.). The author of a musical work is the musician who composes the music and writes the lyrics, whereas the author of a sound recording is the musician who actually records the music (or possibly the record label producing the recording). Thus, for a CD, there are generally two copyrights for every song - one for the musical work, and one for the actual sound recording embodied on the disc.
The category of musical works includes any and all genres of music.