sestet vs musical group

sestet and musical group both are nouns.

Word	Noun	Adjective	Verb	Adverb
sestet	Yes	No	No	No
musical group	Yes	No	No	No

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

Other hypernyms of sestet include musical organisation, musical organization.

sestet (noun)	musical group (noun)
a musical composition written for six performers	an organization of musicians who perform together
a rhythmic group of six lines of verse
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