Kumar Sanu reveals how his singing helped him handle underworld threats during his 90s playback peak, and shares details on his new song with Udit Narayan. Mumbai: Legendary playback singer Kumar Sanu, who has collaborated with his friend, and professional rival Udit Narayan for the song ‘Suniyo Zara’, has shared that he faced threats from the underworld during the peak of his playback career in the 90s.