bagatelle vs piece of music

bagatelle and piece of music both are nouns.

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

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

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

bagatelle (noun)	piece of music (noun)
a table game in which short cues are used to knock balls into holes that are guarded by wooden pegs; penalties are incurred if the pegs are knocked over	a musical work that has been created
something of little value or significance
a light piece of music for piano