Bachchan, 72, who made his debut in playback singing with the song "Mere Paas Aao" in the 1979 film, said the recording process was a "nightmare" for him.
"I was given the sudden news that I was to sing for the first time my own background song 'Mere Paas Aao...' and terrified with the proposition, had battled long hours with the director and the music director that I would not do it because I simply could not. But then that is another story...
"Mr Natwarlal", an action comedy, was directed by Rakesh Kumar and also starred Rekha and Amjad Khan.
Post the singing debut, the "Piku" star did not look back and lent his voice to many songs including "Jumma Chumma", "Khaike Paan Banaras Wala", "Hori Khele Raghuveera" and more recently "Piddly Si Baatein" from "Shamitabh".
"But when it got over, the eminent sound recordist Ghosh babu told me that I should sing more often, and how I had accepted that with a large pinch of salt!!! Not realising how years later and even now the singing continues, giving pain to all its listeners...," Bachchan added.