The Opus 29 Heures Mystiques are made up of 5 each of Entrée, Offertoire Élévation Communion, Sortie and a Verset. These have been arranged into 5 Messe (including a verset in each) and have been uploaded. There are actually 27 Versets in op 29.
Published in 1896, Heures Mystiques is a collection of one-hundred short pieces for organ or harmonium.
Mystique - a quality of being special in a mysterious and attractive way.
Most of these movements do not seem especially mysterious but they are all attractive.
Léon Boëllmann (September 25, 1862 – October 11, 1897) was a French composer of Alsatian origin, known for a small number of compositions for organ. His best-known composition is Suite Gothique (1895), still very much a staple of the organ repertoire, especially its dramatic concluding Toccata.