quartette vs musical group

quartette and musical group both are nouns.

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

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

Other hypernyms of quartette include musical organisation, musical organization.

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