L’Orgue Mystique is a cycle of solo organ pieces composed by Charles Tournemire (1870–1939) for use in the Roman Catholic liturgy. It is subtitled: “51 Offices de L'année liturgique inspirés du chant grégorien et librement paraphrasés” (“51 Offices of the liturgical year inspired by Gregorian chant and freely paraphrased”).
Each office is approximately fifteen minutes in length and consists of five pieces based on the Gregorian Propers for the day:
Using nearly three hundred chants in total, Tournemire created a massive work, which takes over thirteen hours to perform in its entirety.
The word "Mystique" here is very appropriate and the melodic lines of the pieces follow the Gregorian Chants, which are often interwoven between different manuals and voices, while the harmonic structure fluctuates forward and backward from fifths to dissonant chords.
Here I play the office number 7 "Epiphania Domini" matching the liturgical calendar. The score is attached to final piece number 5.