octette vs musical group

octette and musical group both are nouns.

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

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

Other hypernyms of octette include musical organisation, musical organization.

octette (noun)	musical group (noun)
a musical composition written for eight performers	an organization of musicians who perform together
eight people considered as a unit
a set of eight similar things considered as a unit
eight performers or singers who perform together