Belmondo was 14 when he finally took the stage with his accordion joining the big band led by his father and brother Lionel who played saxophone.

When Belmondo arrived in Paris to pursue his career, he met pianist René Urtreger, who gave him many opportunities to share the stage, notably with famed double-bassist Niels-Henning Ørsted Pedersen.

[5] From 1987 to 1990, he played with pianist Kirk Lightsey's quartet and bassist Pierre Boussaguet's quintet, which also featured his brother and Jacky Terrasson.

Working with Boussaguet led to the release of an album called Jazz aux Remparts featuring one of Belmondo's idols, the American trumpeter Tom Harrell.

During his stay in New York, he played with many musicians, including Al Foster, Mark Turner, Lew Tabackin, Donald Brown, and Franck Amsallem.

Belmondo was also part of the development of new bugle and trumpet models which are marketed under the name "Concept TT" by the instrument maker Selmer.