Pope Gregory the Great was the one who strengthened church as an institution. In his time the Roman Catholic church had spread from Northern Europe to northern Africa. In such a huge area an uncontrolled production of liturgical hymns affected by local musical traditions had been observed. This phenomenon had created an impression that churches under the jurisdiction of the Roman Catholic Church were being splitted. So it had to be clear that this was not happening. Gregory codified the liturgical hymns according to the Roman Catholic church calendar . Thus revised sacramentaries were created and western liturgy acquired distinct characteristics that set it apart from the traditions of the eastern liturgy . Pope Gregory is not known to have written something included to the Gregorian repertoire.
"sacramentaria" are old books containing Pope's speeches concerning the liturgy of the Eucharist and other liturgies. Pope Gregory also perfected the alphabetical notation.
Till nowadays, Gregorian chant remains the Roman Catholic Church's traditional music. It consists of 3000 works, all Chants. A Gregorian melody consists of two monophonic phrases sung a capella.
The standard book is called Gradual. Some texts, like Psalms and readings, come straight from the Bible, while others (Kyrie,Te Deum) come from other sources.
During 13th century, because the music was transmitted more through the oral tradition rather than written, the Gregorian style had been forgotten; verses were being translated like a text with long unified note values. The term "cantus planus" has to do with this phenomenon. Neumatic notation was used for Gregorian chant.
Since the end of the Gregorian era the medieval music's period is considered to arose. It lasted up to c 1400 AD.
Hοw Gregorian hymns are sung
1) antiphons. There are two choirs to sing alternately.
2) responsio. There is a solo sung by one voice and a refrain sung by the chorus.
jubilus is a long Melisma placed during the last syllable of the word "Hallelujah" as it is sung in Gregorian chant. During fasting (like Lent) the "hallelujah" was replaced by "passages" or "sequences" which were small groups of psalms with lyrics.
alleluia with jubilus and troped kyrie