I think he didn't want singers to get to fancy with individual variations and distract from the purpose of the mass.
Gregorian chant
Gregorian Chant
Pope Saint Gregory the Great had plainchant renamed "Gregorian Chant" after him.
The Middle Ages were around the time of Pope Gregory I from where Gregorian Chant gained its name
None, Pope Gregory promoted plain song, which, later, became know as "Gregorian Chant" due to his patronage. But, he did not begin it, it already was in the Church for centuries, and is rooted in the Jewish chant used in the synagogue.
Gregorian Chant named after Pope Gregory the Great who compiled all the chants that were being used at the time.
There have been 16 popes named Gregory. Please be more specific.
Pope Gregory founds schola cantorum Schools for church music are established Gregorian chant established as the standard Development of neumes
Gregorian chant is the central tradition of Western plainchant, a form of monophonic liturgical music within Western Christianity that accompanied the celebration of Mass and other ritual services. Although popular belief credited Pope Gregory the Great with having personally invented Gregorian chant scholars now believe that the chant bearing his name arose from a later Carolingian synthesis of Roman and Gallican chant, and that at that time the attribution to Gregory I was a "marketing ruse" to invest it with a sanctified pedigree, as part of an effort to create one liturgical protocol that would be practised throughout the entire Holy Roman Empire.
Pope Gregory the Great loved liturgical music and compiled all the chants that were being used throughout the Church. Later this music came to be called Gregorian Chant in his honor.
The Pope you are probably looking for is Pope Saint Gregory I ("the Great") (c 540-604) who became pope in 590.
Pope St. Gregory the Great is the patron saint of singers and choirs because he is the one who compiled and advanced Gregorian Chant (named after him).