Final answer:
The texture of Gregorian chant is monophonic, characterized by a single melody line. This style was prevalent in the early medieval period before the development of polyphonic music in the later medieval era.
Step-by-step explanation:
The texture of Gregorian chant is known to be monophonic. This means that the chant consists of a single melodic line without an accompaniment or multiple parts or voices singing different melodies at the same time. During the medieval period, particularly in the earlier stages, Gregorian chant was the prevailing liturgical music in the Christian church and it was characterized by this singular melody line that was sung in unison by the choir. Over time, however, the complexity of music evolved and the high medieval era saw the development of polyphonic genres. This shift, often associated with the Ars nova period, brought about the creation of music with multiple independent melodies played or sung simultaneously.