Indeed, when the most holy Gregory poured forth prayers to the Lord, that he might give him the gift of music for the chants, then the Holy Spirit descended upon him in the likeness of a dove, and enlightened his heart; and so at last he began to sing, saying thus: Introit To thee have I lifted up my soul; in thee, O my God, I put my trust; let me not be ashamed. Neither let my enemies laugh at me: for none of them that wait on thee shall be confounded. Psalm Show, O Lord, thy ways to me, and teach me thy paths. Glory be... To thee...” (The Introit for the First Sunday of Advent, preceded by a Trope of the 11th or 12th century. The trope reflects the ancient tradition that Pope St Gregory the Great established the order of chants for the liturgical year in the Roman Rite.)
Sanctíssimus namque Gregorius cum preces effúnderet ad Dóminum ut músicum donum ei désuper in carmínibus dedísset, tunc descéndit Spíritus Sanctus super eum, in spécie colúmbæ, et illustrávit cor ejus, et sic demum exórtus est cánere, ita dicéndo: Introitus Ad te levavi animam meam: Deus meus, in te confido, non erubescam: neque irrideant me inimici mei: etenim universi qui te exspectant, non confundentur. Ps. Vias tuas, Domine, demonstra mihi, et semitas tuas edoce me.