Renaissance music. Is that Gregorian Chant?
No, but much Renaissance music is based on earlier chant melodies. Gregorian chant, also called Roman chant or plainsong, is simple unaccompanied and unharmonized melodies with very little rhythmic variation, as sung by monks. The chants date from the earliest centuries of sacred music, even going back to pre-Christian chanting of the Hebrew scriptures. Chant is about the most primitive music you can hear today. During the Renaissance (maybe the 15th and 16th centuries), polyphonic music (the name means “many sounds”) became highly developed and was the dominant form of religious music in Europe. In polyphonic music, each voice (soprano, alto, tenor, bass, etc.) sings an interesting melodic line, with rhythmic complexity, and the voices intertwine to make a complex weaving of sound. But chant was still in use at the same time, as it is today, and many Renaissance polyphonic compositions include chant as part of their structure.
