The distinction may be applied to everything that exists at once in the scientifically measurable world of vibrations and in the sensibility of the perceiver.
Josef Albers applies the terms to color. In Interaction of Colors he provides countless demonstrations of colors as actual, as they affect one another, in other words, of their mutability.
My work, Tonal Refraction, seeks to do this with tone. Though, as Albers also notes, color and tone are analogous, in one respect they are entirely different. A musician responds to tone specifically, i.e., in terms of a particular instrumental timbre, context within a key, and also memory and association. Every single time the musician plays a given tone all of those factors come into play but never in a predictable comixture; every action of tones is subject to constant variation.
Add to this the remarkable power of a given composition to utterly transform a tone within the range of the composition itself--perhaps one reason why sonatas and symphonies have to have several movements.
