septet vs gathering

septet and gathering both are nouns.

Word	Noun	Adjective	Verb	Adverb
septet	Yes	No	No	No
gathering	Yes	No	No	No

As nouns, gathering is a hypernym of septet; that is, gathering is a word with a broader meaning than septet:

Other hypernyms of septet include assemblage.

septet (noun)	gathering (noun)
a musical composition written for seven performers	the social act of assembling
seven people considered as a unit	the act of gathering something
a set of seven similar things considered as a unit	sewing consisting of small folds or puckers made by pulling tight a thread in a line of stitching
seven performers or singers who perform together	a group of persons together in one place
the cardinal number that is the sum of six and one