Lauda Sion

Lauda Sion Salvatorem is a sequence prescribed for the Roman Catholic Mass of The Solemnity of the Most Holy Body and Blood of Christ. It was written by St. Thomas Aquinas around 1264, at the request of Pope Urban IV for the new Mass of this Feast, along with Pange lingua, Sacris solemniis, Adoro te devote, and Verbum supernum prodiens, which are used in the Divine Office. The hymn tells of the institution of the Eucharist and clearly expresses the belief of the Roman Catholic church that the bread and wine become the body and blood of Jesus during the celebration of the Eucharist. Transubstantiation is the name given to the process in the Roman Catholic faith. As with St. Thomas' other three Eucharistic hymns, the last few stanzas are often used alone, in this case, the Ecce panis Angelorum.

Lauda Sion is one of only four medieval Sequences which were preserved in the Missale Romanum published in 1570 following the Council of Trent (1545–63)—the others being Victimae paschali laudes (Easter), Veni Sancte Spiritus (Pentecost), and Dies Irae (Requiem Masses). (A fifth, Stabat Mater, would later be appointed in 1727.) Before Trent, many feasts had their own sequences. It is still sung today, though its use is optional in the post-Vatican II Ordinary form. The Gregorian melody is borrowed from the 11c sequence Laetabundi iubilemus attributed to Adam de Saint-Victor.

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