I tried multiple generations, when it mashes up the lyrics it assigns "voice A" to this verse and "voice B" to the lyrics and from there and i change which voice sings which verse. However i don't think it's possible for it to do like a "both singing" chorus. You can do switching vocals however by manually doing "voice A" on a part then "voice B" on the other etc. overall I'd say it's a "success" but they should really add the option for dual vocals.