The decaying motion of the plot fills in the shapes with their spiralling-in echo. Encyclogram can also draw the curves in varying colors against a black background. Frequency generally has the greatest effect, controlling the number of lobes. Amplitude controls the lobe sizes.
Phase controls lobe orientations.
Spiro gangs the x and y amplitude and frequency controls, and sets the phases for symmetric spirographs. Decay makes the curve spiral inwards. Color sets a black background, and draws the picture in color. Thick draws a thick line. This also slows the drawing speed.