With a long list of hit songs, including "Sandese aate hain", "Abhi mujh main kahin", "Aal izz well" and "Zoobi doobi", the 39-year-old believes that after a point singing is not about fame, but achieving milestones.
"There is no end to music, you can keep exploring, and there is never an end to it. After a point you don't work for money or fame, you work for milestones. Like 'Kal ho naa ho', 'Main hoon na' have become the biggest milestones," Sonu told IANS.
Nowadays multiple singers sing for a movie album.
"I feel if you have a hero then usually sticking to one voice stays longer. Raj Kapoor had Mukesh, Dilip Kumar had Mohammad Rafi or Talat Mahmood, usually they used to stick to one fixed voice," said Sonu.
However, he feels "there is no hard and fast rule to it".
"It depends on what the album demands. If the film needs multiple genres and if they feel they are happy with multiple voices, then it's okay," he said.
Asked what kind of music he identifies with, Sonu said: "Music is a part of me. I like different genres but all kinds of music is my kind of music."
He will be heard in "Singh Saheb The Great" and "Kaanchi".