Gregorian Chant was adopted by the Christian Church in about the 6th century and chant singing quickly became an essential part of Christian worship. This style of chanting was named after Pope Gregory the Great, who unified all the chants into one collection. It soon became an essential part of monastic worship; and, monks would write new chants and take them from monastery to monastery. Eventually there was sufficient Gregorian Chant for all the services: approximately nine a day, seven days a week and even more on great feast days. In the early days the chant wasn’t copied into books. It had to be memorized and it would take monks many years to learn all the different songs. Eventually they worked out a way to write music down, and words and notes were copied into one large book which all the choir monks would gather round and sing from. 

Many different styles of performance came into being and it wasn’t until the 19th century that the monks, like Gregory the Great, began to seek a single method of performance which reflected what was known about early methods of chant singing. 

There’s a famous monastery at Solesmes in France, and its monks became responsible for the restoration of Gregorian Chant as we hear it today, on CDs and radio. They worked out a very artistic method of singing it and a new method of writing it down. They then produced books which contained the fruits of their scholarship. Their theories were adopted by monasteries throughout the world. 

Unfortunately Gregorian Chant has now largely fallen into disuse in the Catholic church because of widespread change in the services.