What term describes a group of singers or the music written for them?

The term that describes a group of singers or the music written for them is "chorus." A chorus typically refers to a larger group of singers who perform together, often as part of a larger musical work. The term can also refer to the section of a song that is repeated and often features the main theme or message of the piece, which may involve the singers harmonizing.

While "choir" refers specifically to a group of singers, especially within a religious context, it is often used interchangeably with "chorus" in a general sense but predominantly refers to the choral group itself rather than the music. "Ensemble" is a broader term that encompasses various types of musical groups, including vocal performers but also instrumental groups, whereas "band" usually denotes a group that primarily performs instrumental music. Thus, "chorus" captures both the concept of a singing group and the specific musical compositions designed for such a group more accurately in the context provided.