This is how a choir made up of non-music-majors works. First, people have to learn their parts. To learn their parts, most members have to hear them repeatedly. This used to mean that somebody made tapes or CD's of the individual parts. We listened to them at home or in the car until we had our parts down.

At rehearsals we bring it all together and refine it.

With luck, one can find a part online and spare the director the task of making those learning CD's.

A few people might be able to teach themselves using a piano, but most need to hear a recording of some kind.