From TFA:

Oscilloscope Music is music that creates it's own visuals.

The same signal that goes to the speakers is also fed into an analog oscilloscope to draw green glowing lines.

The left and right audio channels correspond to the horizontal and vertical axes of the image.

Parametric functions are meticulously crafted to create synesthetic geometries in a lab aesthetic that is retro and futuristic at the same time.

The tricky part is to create images that sound good and vice versa, which demands novel methods of synthesis, mixing and mastering.

This is exactly was TFA does.