Plainsong, a body of traditional chants used in the Roman Church, is monophonic, consisting of a single, unaccompanied melodic line in free, rather than measured, rhythm. Althought the Proper of the Roman rite (that part which changes according to the date) was settled around the end of the 7th centruy, regional variations in chant style were common throughout the Latin West. This all changed when Pepin, King of the Franks, began the process of imposing Roman chant on the Guals, a process completed by his son Charlemagne, who, once elevated to Holy Roman Emperor in 800, aggressively spread Roman chant throughout the empire to consolidate religious and secular power. Thus, by unifying liturgical practice, a cultural community began. No longer did each tribe and region celebrate Mass in its own way. Suddenly, "European" culture was born, and the course of Western music history was forever changed. As a result, musical notation for chants was now written down.