Gregorian chant takes its name from the Benedictine Pope Gregory the Great (pope from 590 until his death in 604).
He is credited with the reorganization and collection of liturgical chants that had been passed down orally until that time.
In doing so, a need arose to use signs that would help the singer remember the melody, which had been passed down orally until that time. This eventually led to a system of notation on a four-line staff, with neumes (square notation).
Gregorian chant is sang a cappella, without musical instruments, and is monodic (performed with voices singing in unison). Its purpose is to help internalizing the sacred text and meditating on the Word of God.
The large size of the displayed choir books is due to the need for the Schola Cantorum (the choir members) to read all from the same volume held on a badalone (lectern) placed at a long distance.
