B2d) Parallel and Opposite Motion
Color changes move clockwise or counterclockwise when traced on the color wheel.
This is only untrue for changes between perfectly compimentary colors.
(Referring to the color wheel in section B2c - Hard and Soft Changes.)
The object and surround colors have Parallel motion when they proceed in the same direction around the color wheel. In the first example both areas move counterclockwise at the same rate. The colors are chasing each other with the surround a little ahead.
In the next example the surround color is cycling somewhat faster than the object, causing a chromatic penetrations about every four cycles.
With Opposite motion there will be a penetration event about twice in every color cycle. In the example, the surround is still moving counterclockwise, but the circle is moving clockwise.
Comment: While playing chromaccord it is helpful to be aware of clockwise and counterclockwise color progressions, but, as you can see in the examples above, an observer may have to analyse a color change to know its direction. Everyone knows immediately when when a musical scale ascends or descends. This difference in perception is further indication that vusic schemes that rely on hue/tone correlations will be unsatisfactory.
B2e) Drop-out and Replacement