Sonaak KroinlahWell I'd say all of them but when they cut down songs on TV they usually do verse 1, chorus, bridge, final chorus (technical terms?).
And I mean how do you plan to get additional voices when pretty much no one on the site is in the same location?
For the voices, I will record in a key that is hopefully accessible to everyone. I will post that recording online for people to access. From there, I hope I can find a solution that people can use to record their own voices, but that will probably require they know what they're doing...
The simplest thing to do is have them listen to the song in their headphones and record their voice in whatever recording software they want. I'm currently trying to find a free online resource for this, though.