The Ascension Introit fragment also introduces us to the second element of chant discipline-the melodic shape. Most plainsong phrases are images of the underlying word-phrase, and have a parabolic shape. Note that the Introit phrase begins at a low pitch, rise in steps and short leaps to a high point in mid- phrase, and then falls off toward the end. Skilled chant singers emphasize this shape by a crescendo of volume to the peak of the phrase, followed by a decrescendo to the end. The monodic nature of chant is its third distinguishing feature.
Monody is an essential part of the chant discipline.
It is sometimes confused with monotony. The melodies became more melismatic, more decorative, over time. New melodies were developed as new texts became available. But there is not one shred of evidence that harmonization of chant was used in the Western Church before the rise of organum in the early Medieval period. When sung up-tempo in a resonant setting, such as a stone chapel without absorbent acoustical tiles, each series of notes lingers momentarily, blending with its neighbors in thirds and fourths, and generates an ethereal effect.