Nouns

(n)quartet, quartettefour performers or singers who perform together
(n)quartet, quartette, quadruplet, quadruplea set of four similar things considered as a unit
(n)quartet, quartette, foursomefour people considered as a unit“he joined a barbershop quartet”, “the foursome teed off before 9 a.m.”
(n)quartet, quartettea musical composition for four performers