During his piano studies he befriended Federico García Lorca,[1] Salvador Dalí, Buñuel, Rafael Alberti (some of whose poems he set to music) and other Residencia de Estudiantes guests.

[3] In 1927 he composed a ballet, Fandango del Candil, for Spanish dancer Antonia Mercé, La Argentina, and accompanied her on a European tour.

In 1929 he moved to Paris where he studied under Paul Le Flem of the Schola Cantorum and served, until 1934, as manager and secretary to the Spanish painter Néstor.

In 1933 he became an employee of the Spanish section of Paramount Pictures, and continued in that role, after returning to Madrid, at Fono-Espana, Inc., where he dubbed and scored films[4] for the Latin American market.

[12] In March 1939, when Franco's troops had reached Valencia, Durán escaped from Gandia, Spain, aboard a British destroyer, landing at Marseille and, eventually, London.

In 1951, Senator Joseph McCarthy, drawing on a report written for the Spanish Falangist journal Arriba (Madrid), denounced him as a communist and member of the Communist-dominated military intelligence, SIM.