"What a difference a melody makes... the age of melody in song has long gone by... today we have sound, and beat and accompaniment but the melody is missing. I speak of the scenario that I work in - the Indian Film Industry!" he wrote on his blog.
"So Shekhar, of Vishal and Shekhar, have composed something that caused each one that heard it, the goose phenomena. They want me to sing it! And this is where things shall go horribly wrong.
"I am trying to resist this compulsion from them and find myself losing at the moment, but I know for sure that I will remain in that state and lose. May god help all the music purists in bearing up with me and for overlooking this great farce that is about to take place, " he posted.
Shekhar also took to microblogging site Twitter to say that he was honoured to work with Amitabh.
"Sir, it's an our honour to be jamming with you. Means a lot, " he wrote
Amitabh has been singing in films for a long time. Some of his popular songs are "Mere angane mein", "Rang barse" and "Mere paa" among others.