etude vs piece of music

etude and piece of music both are nouns.

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

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

etude: a short composition for a solo instrument; intended as an exercise or to demonstrate technical virtuosity
piece of music: a musical work that has been created

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

etude (noun)	piece of music (noun)
a short composition for a solo instrument; intended as an exercise or to demonstrate technical virtuosity	a musical work that has been created