Interesting and informative. But 8 minutes too long - the woman should talk faster.
I recall seeing a mechanical machine (no electrical parts) in the Science Museum in London. There was a place to hold a sheet of paper with a printed graph of a waveform. There was a sort of stylus (linked to levers) that you would use to trace over the waveform and the machine would draw (on other pieces of paper) the first 3 (I think) harmonics of the waveform. Mechanical Fourier analysis.
...R