He wrote songs until the 1960s, sometimes under an alias, for Dalida, Gloria Lasso, Luis Mariano and Tino Rossi. He worked with lyricist Michel Vaucaire. In 1956 they wrote Non, je ne regrette rien, recorded in 1960 by Édith Piaf. That led to more than 30 songs for her, such as Flonflons du Bal, Mon Dieu and Les Amants which Piaf and Dumont wrote and sang together in 1962.Dumont tells in the book Édith Piaf, Opinions publiques, by Bernard Marchois (TF1 Editions 1995), that Michel Vaucaire's original title was "Non, je ne trouverai rien" (No, I will not find anything) and that the song was meant for the popular French singer Rosalie Dubois. But, thinking of Édith, he changed the title to "Non, je ne regrette rien" (No, I Regret Nothing).