He studied at the Paris Conservatoire from 1942, his teachers included Georges Dandelot for music analysis, Nadia Boulanger for harmony, Noël Gallon for counterpoint and fugue, and Henri Busser for composition.
In 1963, he was appointed director of the École normale de musique de Paris, succeeding Alfred Cortot and working alongside such musicians as Nadia Boulanger, Georges Dandelot, Alfred Desenclos, Norbert Dufourcq and Marguerite Roesgen-Champion.
Petit composed operas, operettas and ballets, orchestral works, concertos, chamber music and songs.
He married the singer Christiane Castelli, famous for her interpretation of Tosca at the Opéra de Paris.
Later he married the violinist Marie-Claude Theuveny in 1958, and had two children with her, Carolin Petit, composer and arranger of music for film and television, and Nicolas.