In this time he also wrote film music for the short films Terreur en Oklahoma (1951) and Chicago Digest (1952).
Longnon created a jazz class on the initiative of Pierre Barbizet at the Conservatoire National Ă Rayonnement Regional (CNRR) in Marseille in 1963.
Philippe Renault, who succeeded Guy Longnon at CNRR in Marseille in 1992, founded the jazz group D6, which recorded a tribute album in honor of Longnon in 2013, Kind of Guy.
Guy Longnon is the uncle of Jean-Loup Longnon.