He was a student at the Paris Conservatoire, where he studied the viola with Maurice Vieux and the history of music with Norbert Dufourcq.
With this ensemble he revived old French music including that of Guillaume de Machaut and André Campra, and played modern works by composers from Bartók to Georges Migot, Charles Koechlin and Jean Françaix.
[1] His first book on the composer was published in 1982 – a 214-page, bilingual French and English "musical iconography" illustrated with numerous photographs, drawings and paintings of Chabrier and his circle.
[11] Away from his usual specialism of Chabrier, Delage was jointly responsible with the Fauré scholar Jean-Michel Nectoux for the first authoritative published text of the 1893 version of Faure's Requiem, smaller in scale and more sparingly orchestrated than the familiar 1901 score.
[2][12] Some recordings exist of Delage's work as a conductor, including music by Chabrier from Une éducation manquée, Fisch-Ton-Kan and Vaucochard et fils Ier.
6, in F major and Georges Migot's Symphonie pour orchestre à cordes, both with the Collegium musicum de Strasbourg,[15] Delage wrote a few pieces of music, including a Scherzo for Cello and Piano, published in 1970.