"I work tomorrow on the 'Bol Bachchan' song, one that I have been asked to sing and perform on. I have through the years discovered that lip syncing your own singing can be most tormenting," the 69-year-old posted on blog bigb.bigadda.com.
Amitabh, who is making a cameo appearance in the movie, will recreate the iconic song "My name is Anthony Gonsalves" by popping out of a life-sized egg for the movie.
"Song and dance have always been a major crisis for me. Moving singing expressing among some exquisite professionals, makes you feel so inadequate and useless. Here in song, with the broadest smile, giving impression of great fulfilment and happiness can be one of the most fake expressions ever devised by actors," he further added.
The movie is slated for a July release.