intermezzo vs piece of music

intermezzo and piece of music both are nouns.

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

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

intermezzo: a short piece of instrumental music composed for performance between acts of a drama or opera
piece of music: a musical work that has been created

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

intermezzo (noun)	piece of music (noun)
a brief show (music or dance etc) inserted between the sections of a longer performance	a musical work that has been created
a short piece of instrumental music composed for performance between acts of a drama or opera
a short movement coming between the major sections of a symphony