CyberBass tracks for each part of :-
These let you listen to the whole thing, or just your part with the others in the background.
What's more, you can try it at anything from 25% above the correct speed to half speed.
Choralia tracks for each part of :-
Much the same as above but with synthesized voices and you can go 50% faster.
If you know and like any others, please let me know and I'll add them,