Usage patterns
〈人〉とコーラスを組むto form a chorus/singing group with someone
I formed a chorus group with my neighbors, and we practice every week.
コーラスに参加するto join a chorus (as a member)
I decided to join the university chorus.
コーラス部に入るto join a chorus club (e.g. at school)
I joined the chorus club in high school and sang many songs.