Palm Sunday
Recessional hymn: O Sacred Head Surrounded, 837
Kyriale: Mass XVII, 762; Credo VI, 788
Hymn after Offertory: Vexilla Regis, Chant
Communion Antiphon: Pater, Si, Heinrich Isaac
During Passiontide and on September 14, the hymn Vexilla Regis is sung during Vespers. This hymn was written by Venantius Fortunatus (530-609) who wrote it in honor of the arrival of a large relic of the True Cross which had been sent to Queen Radegunda by the Emperor Justin II and his Empress Sophia.
Pater, Si, set to music by Heinrich Isaac, derives the melodic material directly from the Gregorian antiphon. In the musical tradition of singing the Passion narratives, as we hear at Mass today, Jesus has the lowest voice. In this motet, which takes the text from Our Lord in the Garden of Gethsemane, the voices are all set lower than an average Communio by Isaac—perhaps as a connection to this tradition.
Heinrich Isaac (c.1450–1517) was a Renaissance composer from the South Netherlandish region. His output was rivaled only by Orlandus Lassus in number and variety of composition. Most notable of his collections is Choralis Constantinus which contains nearly 400 Gregorian chant based motets of propers for the Mass.