Formal:
* Chorus: This is the most common synonym, especially in classical music.
* Vocal ensemble: This emphasizes the group's vocal nature.
* Cantata: This refers specifically to a large-scale choral work.
* Polyphony: This refers to a musical style that uses multiple independent voices.
Informal:
* Singing group: This is a general term for any group that sings together.
* Singing society: This is a more formal term for a singing group.
* Harmony group: This emphasizes the group's focus on singing in harmony.
* A cappella group: This refers to a group that sings without instrumental accompaniment.
Other options:
* Choir can also be used as a synonym for choirmaster or conductor.
* Glee club can be used more generally to refer to any type of singing club, including one that performs pop music or musical theatre.
The best synonym will depend on the specific context and the type of singing group you are referring to.