Final answer:
Pope St. Gregory the Great significantly enhanced the Church's liturgical worship through the establishment of Gregorian Chant, a form of plainchant that has deeply influenced both Christian worship and Western music.
Step-by-step explanation:
Pope St. Gregory the Great, who was pope around the turn of the seventh century, made a significant contribution to the Church's liturgical worship that is still recognized today. This enhancement is widely known as Gregorian Chant, which is the body of liturgical music that takes its name from him and has played a vital role in the Roman Catholic liturgical tradition.
While some historians debate the extent to which Gregory himself wrote these chants, there is no doubt that his influence helped codify and spread this particular form of plainchant across the Western Church, which notably improved the unity and spiritual depth of the Christian liturgy. Additionally, Gregorian Chant laid the foundation for the development of Western music and has had a lasting impact on the history of music as well as liturgical practices.
In contributing to the spreading of Christianity, Gregory also undertook efforts to strategically create alliances with political powers, and through peaceful means like missionary work, he worked to establish and affirm the Church's influence throughout Europe.