are you talking about auditioning vocalists, or auditioning musicians?
for vocalist auditions, we typically have them come out to a rehearsal. They go into their section ( if they don't know whether they are an soprano, alto, or tenor then that is a BIG hint) and sing with the section. After rehearsal we ask the section leads and the director how they felt about it. Praise team is a little different than mass choir because the numbers are fewer and that means everyone has to be able to hold a note. Mass choir we allow anyone who wants to sing to participate ( as long as they come to practice ). Praise team, you have to be invited. is there some drams surrounding this, sometimes. but when they play back the audio and a single person is sticking out like a sore thumb, that usually handles all of the drama.
For musicians, we provide them with a track, a lead sheet, and sheet music ( if they claim to read sheet). they come to the musician rehearsal and perform accompaniment with the track, and solo with the lead sheet and sheet music. if they pass that, we give them a copy of the music for the next rehearsal and ask them to come back. typically musicians that have experience playing in a band setting have no problem.
Jlewis