How did heighted neumes make pitch relationships clearer?

In the evolution of musical notation, early neumes served primarily as memory aids for singers who already knew a melody by heart, indicating only the general rise and fall of the voice.12

"Heighted," or "diastematic," neumes made pitch relationships clearer by being spaced vertically on the page in relation to one another. By positioning the neumes at varying heights, the notation formed a continuous graph of pitch over the text. This spatial arrangement allowed singers to visualize the melodic contour more accurately than with staffless, or chironomic, neumes.21

This development was a crucial step toward modern sight-reading, as it provided a more precise visual representation of melodic intervals. Eventually, this practice evolved into the use of horizontal lines as a grid, which further refined pitch accuracy by establishing specific reference points for the scale.2