Popp was born into a family of German-Dutch background, in Fontenay-le-Comte, Vendée. He started his career as a church organist, filling the place of the abbot who had been called up to serve in World War II in 1939. Popp studied music at the Saint Joseph Institute. In the 1950s he worked for the French radio station RTF, composing music for the "Club d'Essai" and, from 1953 to 1960, "La Bride sur le cou". He orchestrated a number of Juliette Gréco albums in the late 1950s and early 1960s. In the 1960s, he co-wrote, with Pierre Cour, three songs for the Eurovision Song Contest: "Tom Pillibi", which won the competition for France when it was sung by 18-year-old newcomer Jacqueline Boyer in 1960, "Le chant de Mallory", the 1964 French entry, performed by another newcomer, Rachel, and "L'amour est bleu" (Love is Blue) which came fourth for Luxembourg in 1967, but which later became a number-one hit instrumental in the US for Paul Mauriat.