The Eucharist, esp. in the Roman Catholic Church.Music: Certain parts (prayers and formulas) of the liturgy are sung during the service. A differentiation is made between the Proper and the Ordinary. The Ordinary encompasses the liturgical texts that stay the same for every Mass: Kyrie, Gloria, Credo, Sanctus, Agnus Dei. The texts in the Proper do not stay the same but are altered to fit the occasion. When referring to the Mass in a musical sense, it almost always concerns the five parts of the Ordinary. Beethoven wrote two Masses, C major, op. 86 and the Missa solemnis, op. 123.