Harmonies and Near Harmonies

I was having more fun today reading about harmonic ratios, harmonographs, and combining signals that are nearly harmonic but not quite. I recorded this video (sorry about the light static in the audio). In GnuRadio, I am generating two audio tones and feeding them into a scope block in XY mode, while adjusting the second frequency. Slightly discordant frequencies generate a “beat” from the drift in and out of phase with the first signal.