noun
Refers both to the ensemble of four string players (two violins, viola, cello) and to a piece of music written for that ensemble.
彼は弦楽四重奏を結成した。
He formed a string quartet.
モーツァルトの弦楽四重奏を聴くのが好きです。
I like listening to Mozart's string quartets.
Compound of 弦楽 (string music) + 四重奏 (quartet, literally 'four-fold performance').