There are arguments concerning the proper use of the term "Gregorian" in reference to chants. Generally the term refers to any chants written in the church modes, often employing texts from the psalms or the gospels. They developed during the papacy of Gregory the Great (d.604) but generally refer to the Church music of the 11th through 13th centuries. There is a distinction between Roman and Gregorian chants that obfuscates the origin and characterizes true Gregorian chant (that which developed with Gregory I and Gregory II), and Roman chants. There certainly are distinctions that scholars have drawn; however, the distinctions most accurately refer to different styles than to two different types of chants. The Gregorian chant contained phrases that are aesthetically pleasing to the eye often in the form of arches. Musical strains were often related to the text in the context of the contours of the musical line and what the text is addressing. Clearly there was also a balance between melisma and syllabic writing without an over abundance of the former. Though there were exceptions to the eight Church modes, most Gregorian chants were written in that vein. ~ Keith Johnson, All Music Guide