idyll vs piece of music

idyll and piece of music both are nouns.

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

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

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

idyll (noun)	piece of music (noun)
a short poem descriptive of rural or pastoral life	a musical work that has been created
a musical composition that evokes rural life
an episode of such pastoral or romantic charm as to qualify as the subject of a poetic idyll