Pope Gregory I in the context of "Æthelberht of Kent"

Gregorian chant is the central tradition of Western plainchant, a form of monophonic, unaccompanied sacred song in Latin (and occasionally Greek) of the Roman Catholic Church. Gregorian chant developed mainly in western and central Europe during the 9th and 10th centuries, with later additions and redactions. Although popular legend credits Pope Gregory I with inventing Gregorian chant, scholars believe that he only ordered a compilation of melodies throughout the whole Christian world, after having instructed his emissaries in the Schola Cantorum, where the neumatical notation was perfected, with the result of most of those melodies being a later Carolingian synthesis of the Old Roman chant and Gallican chant.

Gregorian chants were organized initially into four, then eight, and finally 12 modes. Typical melodic features include a characteristic ambitus, and also characteristic intervallic patterns relative to a referential mode final, incipits and cadences, the use of reciting tones at a particular distance from the final, around which the other notes of the melody revolve, and a vocabulary of musical motifs woven together through a process called centonization to create families of related chants. The scale patterns are organized against a background pattern formed of conjunct and disjunct tetrachords, producing a larger pitch system called the gamut. The chants can be sung by using six-note patterns called hexachords. Gregorian melodies are traditionally written using neumes, an early form of musical notation from which the modern four-line and five-line staff developed. Multi-voice elaborations of Gregorian chant, known as organum, were an early stage in the development of Western polyphony.

The Catholic Church in England and Wales (Latin: Ecclesia Catholica in Anglia et Cambria; Welsh: Yr Eglwys Gatholig yng Nghymru a Lloegr) is part of the worldwide Catholic Church in full communion with the Holy See. Its origins date from the 6th century, when Pope Gregory I through a Roman missionary and Benedictine monk, Augustine, later Augustine of Canterbury, intensified the evangelization of the Kingdom of Kent, linking it to the Holy See in 597 AD.

This unbroken communion with the Holy See lasted until King Henry VIII ended it in 1534. Communion with Rome was restored by Queen Mary I in 1555 following the Second Statute of Repeal and eventually finally broken by Elizabeth I's 1559 Religious Settlement, which made "no significant concessions to Catholic opinion represented by the church hierarchy and much of the nobility."

The Schola Cantorum was the trained papal choir during the Middle Ages, specializing in the performance of plainchant for the purpose of rendering the music in church. In the fourth century, Pope Sylvester I was said to have inaugurated the first Schola Cantorum, but it was Pope Gregory I who established the school on a firm basis and endowed it. The choir ranged anywhere from twenty to thirty boys or men. Only the most skilled in singing were selected to participate in the Schola Cantorum.

The Book of Pastoral Rule (Latin: Liber Regulae Pastoralis, Regula Pastoralis or Cura Pastoralis — sometimes translated into English Pastoral Care) is a treatise on the responsibilities of the clergy written by Pope Gregory I around the year 590, shortly after his papal inauguration. It became one of the most influential works on the topic ever written. The title was that used by Gregory when sending a copy to his friend Leander of Seville. The text was addressed to John, the bishop of Ravenna, as a response to a query from him. Gregory later revised the text somewhat.

The term Last of the Romans (Latin: Ultimus Romanorum) has historically been used to describe a person thought to embody the values of ancient Roman civilization – values which, by implication, became extinct on their death. It has been used to describe a number of individuals. The first recorded instance was Julius Caesar's description of Marcus Junius Brutus as the one with whom the old Roman spirit would become extinct.

Salus Populi Romani (English: Protectress of the Roman people, also known as the Salvific Health of the Roman people) is a Roman Catholic title associated with the venerated image of the Blessed Virgin Mary in Rome. This Byzantine icon of the Madonna and Child Jesus holding a Gospel book on a gold ground, now heavily overpainted, is kept in the Borghese (Pauline) Chapel of the Basilica of Saint Mary Major.

The image arrived in Rome in 590 A.D. during the reign of Pope Gregory I. Pope Gregory XVI granted the image a canonical coronation on 15 August 1838 through the Papal bull Cælestis Regina Maxima. Pope Pius XII crowned the image again for the secondary time and ordered a public religious procession during the Marian year of 1 November 1954. The image was cleaned and restored by the Vatican Museum, then given a Pontifical Mass on 28 January 2018.

Pope Leo I (Italian: Leone I) (c. 391 – 10 November 461), also known as Leo the Great (Latin: Leo Magnus; Italian: Leone Magno), was Bishop of Rome from 29 September 440 until his death on 10 November 461. He is the first of the three Popes listed in the Annuario Pontificio with the title "the Great", alongside Popes Gregory I and Nicholas I.

Leo was a Roman aristocrat. He is perhaps best known for meeting Attila the Hun in 452 and persuading him to turn back from his invasion of Italy, though how large a part his personal authority played is debated, and some argue that Attila was already ready to end his campaign. He is also a Doctor of the Church, most remembered theologically for issuing the Tome of Leo, a document which was a major foundation to the debates of the Council of Chalcedon, the fourth ecumenical council. That meeting dealt primarily with Christology and elucidated the definition of Christ's being as the hypostatic union of two natures, divine and human, united in one person, "with neither confusion nor division". It was followed by a major schism associated with Monophysitism, Miaphysitism and Dyophysitism. He also contributed significantly to developing ideas of papal authority.

The Gregorian Reforms were a series of reforms initiated by Pope Gregory VII and the circle he formed in the papal curia, c. 1050–1080, which dealt with the moral integrity and independence of the clergy. The reforms are considered to be named after Pope Gregory VII (1073–1085), though he personally denied it and claimed his reforms, like his regnal name, honoured Pope Gregory I.