1.
vocal ensemble (duet, trio, quartet, etc.)
Singing in which each part is performed by a single voice, in contrast to 合唱 (chorus) where each part has multiple singers. Used in classical music for duets and small ensembles.
Compound of 重 (layer; multiple) + 唱 (singing). Number prefixes specify the size: 二重唱 (duet), 三重唱 (trio), 四重唱 (quartet).