Solo/Accomp. Contrast
The element of support through adequate volume remains important, even if the organist chooses to emphasize contrast through timbre (tone color). All organ stops come with a set volume and timbre, and the two factors cannot be easily separated. But we can understand each factor independent of the other, then make choices accordingly.
Even very little contrast in timbre is enough to set apart a solo. In two ranks of similar volume, the rank with either a richer overtone structure or one that emphasizes the higher partials will tend to predominate. A hybrid with a slight “edge” will predominate over a flute of similar volume simply due to its greater abundance of overtones. Likewise, a string can serve as a solo against a flute of similar volume because of its abundance of upper overtones.
