” … The melodic thread has an ever-changing but ever-present volume or thickness.”
Continuing through Language of Vision by Gyorgy Kepes (1944):
… Due to the laws of visual organization, no visual unit can exist in itself on the picture-plane. Each unit leads beyond itself and implies a larger whole. Thus units not only live on the picture-plane; they also grow. They merge into wholes with a common function. Three musical tones have each its particular wave length, its individual tonal quality; but when the three are sounded together their individual characteristics retreat and something entirely new appears — the chord.
[line break added] Similarly, the optical units organized into spatial configurations become more than the sum total of their component parts. These larger wholes form with other groups a still farther-reaching unit, and this process continues until all possible relationships are exhausted; that is, until the limit of attention is reached. This law of organization implies, then, that the numerical increase of elements does not necessarily lead to a loss of order of the picture whole. A uniform picture surface is flat.
[line break added] A gradual increase of the elements upon that surface shows clearly that, in each addition to the number or quality of units, a spatial unity can be maintained. Reaching the numerical limit of organization, previously separate units, in a kind of revolutionary leap, form a common figure — and thus a new condition for the organization of a more embracing whole. The number of units can be increased in so far as they do not interface, forming further units. But when this point of saturation is reached, there is no further opportunity for plastic organization. A uniformity of surface is produced on a new level.
… The image as a living experience cannot long exist in a frozen structure. For the image to remain a living organism, relationships within it must be constantly changing. The eye and the mind must be fed with changing visual relationships. Only this changing variety can provide the stimulation necessary for holding attention upon the picture surface.
[line break added] Change implies motion. The plastic image must also be articulated, therefore, in the time dimension. The ultimate aim of plastic organization is a structure of movement that dictates the direction and the progression toward ever new spatial relationships until the experience achieves its fullest spatial saturation.
… Rhythmic organization, although an essential condition for keeping the attention and thus prolonging the life span of the image, is not in itself fully sufficient to secure the maximum endurance of attention necessary for integration of a plastic form. One is well acquainted with the irritating sensation produced by the regular repetition of a sound of a drum. One knows almost instinctively that a simple rhythmic pattern possesses a regularity that soon becomes monotony. If the image is to remain a living organism, the relationship within it must have progressively changing aspects.
… Plastic movement can be repeated in various visual qualities such as color, tone, value, texture, shape, form, and so on. The eye passing from one sensory stimulation to another receives an accumulated impetus which leads it to embrace newer relationships on the picture surface.
Music suggests an excellent analogy. A musical unit played by an instrument is repeated contrapuntally on other instruments, on the strings, on the brasses, on the woodwinds, even on percussion instruments. Each plastic unit with its specific sensory quality echoes the previous one; light, dark, color, shapes, forms, all mutually help one another, one taking over the movement where another stopped, leading toward complete unity.
“The groups of tones in a melody which are harmonically connected are like the links in a chain; they give the melody color and sheen. They are the real body of the melody, strange as it may seem to speak of body in connection with a linear phenomenon like a melody. It must not be forgotten that a melody is only primarily linear, and that the comparison with a curved line applies only to the most obvious, external aspects of a chain of tones. The melodic thread has an ever-changing but ever-present volume or thickness” [Hindemith].