serenade vs piece of music

serenade and piece of music both are nouns.

Word	Noun	Adjective	Verb	Adverb
serenade	Yes	No	Yes	No
piece of music	Yes	No	No	No

As nouns, piece of music is a hypernym of serenade; that is, piece of music is a word with a broader meaning than serenade:

Other hypernyms of serenade include composition, musical composition, opus, piece.

serenade (noun)	piece of music (noun)
a song characteristically played outside the house of a woman	a musical work that has been created
a musical composition in several movements; has no fixed form

serenade (verb)	piece of music (verb)
sing and play for somebody