[phkahler]

>> but you can't see harmonics happening to the string.

But you absolutely can if you rest a finger on a node and pick it, producing primarily the harmonic. You can even see the lesser vibration at the nodes with your eyes.

[kazinator]

If you stretch a rope or chain several meters long, you can simultaneously see the fundamental and first harmonic standing wave.

[geon]

It is fun to kick a guywire and watch the single pulse travel along the wire, be reflected and come back.

[DANmode]

> It is fun to kick a guywire

Way braver than me!