I did this once by singing the same part vocal through a vocoder with the pitch bend wheel held slightly (and randomly) up and down, not even a complete half step, onto 5 other tracks, also running through a digital delay with 5 different slightly different slapback times, muting the original completely. I ended up keeping 3 of the 5.

However, know that I was going for a specific effect of people shouting a refrain in a chorus, and if you want serious pitch control to sound like an ensemble that idea isn't for you. (Think "Boom boom..... out go the lights".)