[1] At aged ten he entered the Paris Conservatoire[2] and completed his musical training in theory, piano and composition, taking in Nadia Boulanger's accompaniment class.

[4] Defaye's primary instrument was the piano, but he also played trombone and trumpet.

[5] He attended the composition classes of Darius Milhaud and Tony Aubin.

[3][7] As a composer he wrote mostly for brass,[3] especially trombone; he wrote pieces for trombone and piano in the style of classical composers such as Bach, Brahms, Debussy, Schumann, Stravinsky and Vivaldi.

[3] He also collaborated with Juliette Gréco, Zizi Jeanmaire and Les Branquignols [fr].