Tandon last made news when he got Asha Bhonsle to record a composition over the Internet for "Page 3".
Dey recently recorded a soulful number for "Umar", produced and directed by Karan Razdan, thanks to Tandon's initiative of tracing the veteran singer and coaxing him to sing for the film.
The last time Dey sang for a film was in 1991 for "Prahaar".
Tandon said he was apprehensive whether Dey would agree to sing. However, the Padma Bhushan recipient was impressed with the retro kind of music that Tandon had composed for "Umar" and consented.
"It was a big achievement for me. I knew that the song would be incomplete without his voice," Tandon said.
"Umar", starring Satish Kaushik, Kadar Khan and Prem Chopra, tells the touching story of three old men fighting the travails of life. There are four songs in the film, one of which is an intense eight-minute ghazal by Jagjit Singh.