aruvi, listen to ARR's voice in: Vellai pookal ( KM) Yeh jo des hai tera (Swades) Lukka chuppi (RDBasanti) Desh mere(legend of bhagat singh) Theeyil vizhunda(Godfather) and then make ur judgement.... its a gud question, actually.....there were unconfirmed reports 4-5 years back that ARR called Bavatharini to sing in a song, but it didn't materialise.......i guess ARR singing for YSR is more possible than YSR singing for ARR.....