Claude Debussy wrote that his work possessed a "fine dreamy musicality", commenting on its characteristically hesitant character by suggesting that it sounded as if it was "afraid of expressing itself too much".

At the age of fifteen, when still a student of the Nantes High School, he wrote a three-act opera Gilles de Retz.

He was admitted to the Paris Conservatoire to study under Gabriel Fauré, learning harmony under Antoine Taudou and counterpoint from André Gedalge.

Like fellow students Maurice Ravel, Florent Schmitt, Louis Aubert, Jean Roger-Ducasse and Georges Enesco, he had become well known before he left the Conservatory.

The ballet La Prêtesse de Korydwenn (The Priestess of Ceridwen) was first performed at the Paris Opéra Garnier on 17 December 1926.

In 1928, Ladmirault published a manifesto of Breton music in the first issue of the Celticist journal Kornog.

[3] Nevertheless, he took the view that Breton folk music was cruder than its "civilised" Irish and Scottish counterparts.