iternabe Playing a set of overtones can create the illusion of the presence of the base frequency note that was not played
Arguably that one is not an illusion. When you add up overtones, they will form a wave similar to the missing fundamental. More overtones you add, more the sum will match the fundamental. It is actually even cooler because any arbitrary wave can be made by adding overtones of varying amplitudes. That's how Fourier transform works.
OK. I will shut up but after this 🙂 : Those transforms are not limited to one dimension (eg. sound waves). Here is a way of applying them to 2D drawings: https://www.dynamicmath.xyz/fourier-epicycles/ I'd like to think each circle on those animations is like an "overtone".