Léo Souris was mainly active as a composer/arranger and conductor, in many different contexts.
He arranged and conducted the strings for performances of Chet Baker, Helen Merrill, etc...(Comblain-la-Tour festival).
He formed bands of various sizes in which some of the finest Belgian musicians played, such as Jacques Pelzer (sax), Herman Sandy (tp), Benoît Quersin, Vivi Mardens, Jo Demuynck, etc...and played in Europe and Africa.
He also wrote for the BRT Jazzorkest, led by Etienne Verschueren.
Later, he hosted a jazz show on the Belgian radio RTB during many years.
He wrote, arranged and conducted in the field of chanson and light music, too (he conducted the orchestra for Fud Leclerc during the Eurovision song contest 1956).