The origins of liturgical music traditionally date back to St. Gregory the Great (d. 604), who was inspired by the Holy Dove to record the principles of 'Gregorian' chant. The Gradual contained the musical parts of the Missal and was sung from the steps (gradus) of the altar. The Antiphoner contained the musical sections of the Breviary. These terms have become interchangeable in modern times. Because of their size and complexity, these manuscripts were still being handmade in the traditional way for centuries after the introduction of printing. They were boldly hand-written and illuminated on large sheets of sturdy vellum so that the entire choir could read from one book.

This sheet is from an antiphonary written in four-line music in black and red ink with five large initials. The song translates in part as:

Alas, alas, my son! So that we sent you to travel, the light of our eyes, the staff
Bless the God of heaven, and confess before all the living that he has shown us his mercy.

References:

Condition: B+

Light soiling and foxing with small remnants of framing tape on verso.