sextet vs musical composition

sextet and musical composition both are nouns.

Word	Noun	Adjective	Verb	Adverb
sextet	Yes	No	No	No
musical composition	Yes	No	No	No

As nouns, musical composition is a hypernym of sextet; that is, musical composition is a word with a broader meaning than sextet:

Other hypernyms of sextet include composition, opus, piece, piece of music.

sextet (noun)	musical composition (noun)
a musical composition written for six performers	a musical work that has been created
six people considered as a unit
a set of six similar things considered as a unit
six performers or singers who perform together
the cardinal number that is the sum of five and one