Moitra started his career as a client servicing executive at an ad agency, while music remained a hobby. He started composing music for advertising jingles accidentally, when he was asked to compose a jingle at the last minute by Pradeep Sarkar, then the Creative Head of the agency. The jingle was "Bole mere lips. I love Uncle Chipps" for the chips brand Uncle Chipps, which became an instant hit. He later composed several jingles for Pradeep Sarkar, and several advertising brands.