There were also things like Michelson's harmonic analyzer: https://www.asme.org/engineering-topics/articles/technology-and-society/return-of-the-harmonic-analy

There were also things like Michelson's harmonic analyzer: https://www.asme.org/engineering-topics/articles/technology-and-society/return-of-the-harmonic-analyzer https://www.asme.org/engineering-topics/articles/technology-...