Passionate about the Bible and liturgy, for a year he was professor of Holy Scripture at the newly established major seminary of Brazzaville, Congo.
Returning to France for health reasons in 1948, he spent decades as a professor and a retiree at the seminary of Chevilly-Larue, which later renamed its library in his honor.
[2][3][4] Deiss composed over 400 pieces of liturgical music, many inspired by Gregorian chant and Renaissance polyphony with biblical texts.
[2] He once described the impetus for his composing career, starting at a small suburban parish in the 1950s: "I realized that the people knew almost nothing of the Bible, so I decided to try using music to help them memorize the more important texts.
[7] He received a Grand Prix de l'Académie Charles Cros for the 2005 album Ave Maria that he recorded with his Chevilly seminary choir.