Balam Pichkari- Vishal's chorus

I'm sure majority of you all have heard balam pichkari, if you haven't then I suggest that you definitely do! Well, basically today I heard the Zero Hour Mashup 2013 by Kiran Kamath. I noticed that in this mashup, Vishal is actually singing the chorus that is sung in all of the actual videos and music tracks by a group of singers or so.

The link to the Zero Hour Mashup 2013 is here: http://www.youtube.com/watch?feature=player_detailpage&v=BhiaLx0fvj4#t=74

Right from there on, listen to the sections from balam pichkari, you'll notice it- Vishal singing a part that he didn't sing in the song.

Does anyone have any idea what is going on here? Is there another version of balam pichkari?

It sounds really good and I'd love to know.

Thank you all!