Pange Lingua

When Pope Urban IV extended the feast of Corpus Christi to the whole church in 1264, tradition records that the office and Mass texts for the new feast were entrusted to Thomas Aquinas, and the liturgy that resulted is commonly counted the most perfect ever composed for a single feast. The Pange Lingua is its Vespers hymn. In six stanzas Aquinas narrates and interprets the eucharist, the word made flesh who at the last supper gave himself to the twelve, fulfilling the law with his own hands, and then the couplet on which the whole theology balances, the word as flesh makes true bread flesh by a word, and if sense fails, faith alone suffices to steady the sincere heart.

The hymn ends by falling on its knees. Its last two stanzas, beginning Tantum ergo sacramentum, let us venerate so great a sacrament with bowed heads, became a liturgical unit of their own, sung at Benediction of the Blessed Sacrament wherever that devotion exists, so that millions who have never sung the full hymn know its ending by heart. On Holy Thursday the full Pange Lingua accompanies the procession that carries the sacrament to the altar of repose, with the Tantum Ergo reserved for the arrival, the one night of the year when the hymn does exactly the work it was written to do.

Aquinas did not invent his opening line. Six centuries earlier Venantius Fortunatus had written Pange, lingua, gloriosi proelium certaminis, sing, my tongue, of the glorious battle, a passion hymn that narrates the cross as a combat and the tree as the trophy, composed in the same trochaic metre that Roman soldiers had once used for marching songs.

Fortunatus's hymn had long been sung in Holy Week, and Aquinas, writing for Corpus Christi, deliberately took up its first words and its metre, changing battle to mystery, proelium to corporis mysterium, so that his eucharistic hymn opens as a quotation his hearers would recognize, the sacrament presented as the continuation of the passion the older hymn sang. The two Pange Linguas have run side by side in the liturgy ever since, the Fortunatus hymn in Passiontide and on Good Friday, where it accompanies the veneration of the cross, the Aquinas hymn at Corpus Christi and Benediction. The borrowed metre had a long afterlife of its own, becoming one of the standard frames of Latin hymnody. Musically the Aquinas text is inseparable from its Phrygian chant melody, whose grave, stepwise motion composers have mined repeatedly, and the Tantum Ergo alone has hundreds of settings, from Mozart's two to Faure's, a devotional repertoire descended at two removes from a late antique battle song.