Synaesthesia is an eyecandy program that represents music graphically in real time as coruscating fields of fog and glowing lines. It is intended as a visual accompaniment to music. Its display combines information about the frequency, location and diffuseness of sound. It can take input from CD, line, piped from another program, or from EsounD. It also functions as a CD player.

One feeling or perception described with words usually used for a totally different or opposite feeling or perception. Ex: "The sky smelled blue." "The soft hum of fog."

A particular example of cross-modal or transfunctional neural action seen, e.g., in the perception by some individuals of colours systematically associated with differing (musical) sounds.

A cross talk effect in the brain in which one sensory pathway links across to another, resulting in two outputs from one input.