(Fr. quatuor; Ger. Quartett; It. quartetto).
A comp. for 4 vv. or instr. or the 4 singers or performers who sing or play such comps. (e.g. Chilingirian Qt.). In the case of perfs., qt. usually implies a str. qt., i.e. 2 vn., va., vc. But there are also pf. qt. (pf. and 3 bowed instr.), ob. qt. (ob. and 3 bowed instr.), etc. In opera, a qt. is for 4 solo vv. (e.g. in the last act of Rigoletto). The vocal qt. for unacc. vv. has existed since mid‐15th cent.