Ten years after writing Les Corps Glorieux (8.573682), Olivier Messiaen developed a plan to compose a Book of Rhythmic Studies for the organ. This resulted in two distinct works of which Livre d'orgue proved to be an anthology representative of his compositional thinking at the time. It runs the gamut of rhythms, tone colours and sonorities, ranging from extreme delicacy to the most powerful vehemence, and includes new modes, complex Hindu rhythms, and an aviary of birdsong. The test piece Verset pour la Fete de la Dedicace offers a more serene vision in its own essay in birdsong.