What is a piece of music written for group singers called?

A piece of music written for group singers is called a chorus or a part-song. A chorus typically refers to a group of singers who sing together, often in a refrain or repeated section of a song. Part-song, on the other hand, is a specific genre of choral music in which each voice part has its own independent melodic line. Part-songs can be sung by mixed voices (SATB), men's voices (TTBB), or women's voices (SSA). Choruses and part-songs are both popular forms of group singing and can be found in a wide variety of musical styles, ranging from classical to contemporary music.