Tomita was born in Tokyo and spent his early childhood with his father in China. After returning to Japan, he took private lessons in orchestration and composition while an art history student at Keio University, Tokyo. He graduated in 1955 and became a full-time composer for television, film and theatre. He composed the theme music for the Japanese Olympic gymnastics team for the 1956 Summer Olympics in Australia.

In 1965, he composed the theme song and incidental music for Osamu Tezuka's animated TV series Jangaru Taitei (Jungle Emperor), released in the USA as Kimba the White Lion. In 1966 he wrote a tone poem based on this music with an original video animation synchronized to the tone poem released in 1991.