This hymn was originally written by St. Ambrose (340-397) for feasts of Martyrs. In its complete form it contained eight stanzas. The hymn ‘Christum profusum sanguinem’, for Martyrs in Paschaltide, is a part of the Aeterna Christi munera. This revised form of the Hymn is used in the Roman Breviary for Matins on feasts of the Apostles and Evangelists and in the Ambrosian Liturgy for Vespers on feasts of the Apostles and Evangelists.
This Hymn has been set to at least 18 melodies (Global Chant Database)
Ambrosian Vespers Hymn
Alternative Melodies for the Dominican Antiphonale
This Hymn is also found in the Roman Breviary used for Matins