Recording her song for a film after long 12 years, Rupa said she was more focused on acting than singing and wondered what convinced the national award authorities to pick her up.
"The song seemed to feel good more because of the visuals, which created the mood, than the quality of my singing," said Rupa.
The 45-year-old actress said her voice was not in proper shape due to back to back shooting and there were far more worthy contenders for the award.
"There were many other contenders who did a better job in other films, I guess," Rupa said at a meet to promote the film, which released today.
The actress said the director and the script-writer were insistent that none but she could do the playback part and for her part she was determined not to bite the bullet.
"I felt like telling them, 'have you all turned mad'? But ultimately I had to give in. They were all so insistent," Rupa recalled.
Probably they were inspired by Rituparno Ghosh who, she said, made her sing in full throated voice in the film 'Bariwali' where she had played the character of a heroine present in a shooting.
She, however, said she could deliver with proper practice and musical accompaniment as she had brought out a solo Rabindrasangeet album in the past.
"It was Rituparno who first made me sing my own number without any musical accompaniment in a film, but he was already a known name at that time unlike Aditi, the director of Abosheshe," she said.
Talking about her role of a mother role in the film, Rupa said, "I initially was not very sure if a young girl like Aditi can handle such subtle issues on celluloid at the outset when she came to me with the script by Neel Mitra."
But ultimately she acquitted herself very well, Rupa said.
'Abosheshey', which had been screened at IFFI Goa, Thiruvananthapuram, Wasghington DC South Asian Film Festivals and some other festivals, deals with the quest of a son (Ankur Khanna) to discover his mother Suchismita (Rupa) and her roots.
About the songs and Rupa's initial reluctance, Aditi said, "We had to assure her that in the event of her voice cracking during recording we would make an alternative arrangement. But nothing of that sort happened as you can see from the audience response to the three tracks by her including "durey kothaye".
Rupa said she has no qualms to play roles of mothers in Bengali films now, since she was also acting as mom in "Na Hanyate" by director Ringo.
About working with Mithun Chakraborty in two films - - the under-production entertainer 'Buddhuram Dhol' and recently released 'Nobelchor' - - Rupa said these were very different portrayals.
"Mithun is a co-actor I would always love to work with. Even when he is not in proper mood he starts cracking jokes," she said.