A polymuse is a person whose expertise spans a significant number of subject areas in the musical arts. In less formal terms, a polymuse (or polymusical person) may simply refer to someone who is very knowledgeable in music.
Someone who is an expert at 3 or more classes of musical instruments (including the use of vocals) may also be called a polymuse.
Someone who listens to wide variety of music genres may refer to themselves as a polymuse though to a much lesser degree due to the fact that the average person listens to wide variety of genres in the first place.
A one man band is a polymuse.
Not to be confused with audiophile
Lance: Avril knows how to play the guitar, the drums, and even the piano. She doesn't sing too bad either. She's quite the polymuse.
Aldrich: You call that singing? Avril is old hat
Abbie: Beethoven is a bit of a polymuse. He plays the organ, piano and the violin but an organ and a piano is in the same class of instruments so...