  In physics, timbre is a complex phenomenon, like color. Musical timbres are
given by the superposition of sinusoidal signals, corresponding to longitudinal
acoustic waves. Colors are produced by the superposition of transverse
electromagnetic waves in the domain of visible light. Regarding human
perception, specific timbre variations provoke effects similar to color
variations, for example, a rising tension or a relaxation effect. We aim to
create a computational framework to modulate timbres and colors. To this end,
we consider categorical groupoids, where colors (timbres) are objects and color
variations (timbre variations) are morphisms, and functors between them, which
are induced by continuous maps. We also sketch some gestural variations of this
scheme. Thus, we try to soften the differences and focus on the similarity of
structures.
