A chord is a set of whole numbers. Play one, and the ratios between its notes decide the shape you see: whole numbers close into a standing figure, and anything else never closes at all. The big scope is the whole chord; under it sits every interval inside it, on its own.
Switch from just intonation to equal temperament and watch which figures stop standing still — that is exactly how far each interval was bent to make a keyboard work.
The picture is the sound. X is the left channel, Y is the right, and the curve is the plot of that pair.
Audio starts on your first click.