Whatever he sang, in whichever style, he poured his heart and soul into it. You could sense his devotion in each bhajan (e.g. man tadapat hari darshan ko aaje), romance or melancholy in his gazals (e.g. baad muddat ke ye ghadi aayi, zindagi bhar nahin bhoolegi), and sheer energy and youthful exuberance in his pop songs ("aaja aaja main hoon pyaar tera" ofcourse, and ek haseen shaam ko dil mera kho gaya). I also think that each one of his tragically few semi-classical songs were gems (e.g. madhuban men raadhika, akhiyan sang akhiyan laagin aaj). What's more, he redeemed songs that might have otherwise been humdrum (e.g. April fool banaya)
