A.R. Rahman is one of India’s best-known music composers, winning multiple Academy Awards and putting Indian film music on the international stage. For his longtime fans, though, Rahman’s early songs from the 90s and 2000s still hold a special place. An upcoming concert called “Retro Rahman” wants to recapture some of that magic by bringing together singers from India who sang many of Rahman’s early hits. We speak to Unnikrishnan, acclaimed Indian classical vocalist and playback singer, about his music and his collaborations with A.R. Rahman.