Alexis possibly initiated the writing of a mass to celebrate the 700th anniversary of the feast Corpus Christi in Liège.

[1] During world War II, Jongen could not compose anything from August 1944, due to the depressing circumstances of his life at the time.

[1] The full title is Messe en l'honeur du Saint-Sacrement, marking it as a mass in honour of the Blessed Sacrament.

[2][3] Alexis inspired several musical features of the Mass, such including elements from Gregorian chant, the inclusion of brass instruments after the model of Giovanni Gabrieli, and writing more counterpoint than before, such as fugato for "Pleni sunt caeli" of the Sanctus, and counterpoint in the voices in the "Cum Sancto Spiritu" of the Gloria and the "Et resurrexit" of the Credo.

[4] The Mass was recorded in 1994 by the Brussels Choral Society and the Luc Capouillez Brass Ensemble, conducted by Tom Cunningham.

[5] It was recorded again in 2007 by St. John's College Choir, Cambridge, the London City Brass and organist Paul Provost, conducted by David Hill.