User talk:Gyandeeprkmv

You asked about harmonographs -- do they have any practical uses? Maybe, maybe not. But some closely-related curves definitely do have some important uses! Consider the use of decorative curves engraved for printing money and stock certificates. These curves can be made arbitrarily complex, so are exceedingly difficult to counterfeit. Dozens of parameters must match, or differences from a counterfeit can be readily detected by comparing with an "authentic" curve.

In a physics lab, I have used an oscilloscope and a calibrated signal generator to match pitches, as in tuning a guitar. Use a microphone to pick up sound from the musical instrument, and feed the signal into the horizontal or the vertical amplifier built into the 'scope. Run the signal from the calibrated signal generator into the amplifier for the other axis. If the pattern on the screen is a stable ellipse, then the frequencies match exactly. If the ellipses drawn on the screen wobble or rotate slowly, the frequencies are close, but not exactly equal. If you see complicated pretzel shapes (these can be interesting and pretty), the frequncies vary considerably.

I actually courted (successfully!) a girl who had a stereo phonograph and a recording of "Switched on Bach" (early synthesizer music with relatively simple wave forms). I connected one wire from the left speaker to control one axis of the 'scope, and a second wire to the other speaker, to control the other axis. A third wire connected to the "ground" connection of the 'scope, to complete both circuits. We saw stars, triangles, spirals, and tic-tac-toe boards on the screen, before we could hear the music which caused them. What girl wouldn't be impressed when you'r firing electrons towards her at 600,000,000 miles per hour! Ray Calvin Baker (talk) 22:40, 1 October 2012 (UTC)