The composition as a whole:
Audio with Score
Midi files are not copyrighted. Several web sites already contain midi files for a wide variety of
choral compositions (e.g., Silvas Woodshed).
See the Resources page for links.
Particular voice emphasized
Particular voice omitted
Particular voice with tempo control (only indirectly compatible with Macs)
Online part rehearsal
Although there is an increasing amount of Midi filies for individual part learning on the web, such files are not typically
found on mega sites. You will likely need to perform a web search for them (e.g., Google). Otherwise, you may record
such files yourself and upload them to your server.