Is first or second chorus same track as third chorus? If so, you can use audacity to align non-adlib chorus to adlib chorus, then invert the fist one.
If it does not work, you can use utagoe (google "how to use utagoe") utagoe is a free software that seperates vocals from a song. To extract adlibs you need to insert adlib chorus as song and non-adlib chorus as instrumental.

If you still cannot do it, tell me the song name and i will see what can i do.