A few days ago I noted with amazement an old spectrogram displayer that was used for training deaf speech. The Maico Chromalyzer was made in 1954 but probably didn’t gain much success.
I couldn’t resist modeling and animating it, using my guess about its innards. This version shows 5 horizontal bulbs, each responding to a bandpass filter. Fortunately I had some Python spectrogram code left over from an unused courseware addendum, and modified it to drive this spectrogram-like device.
Spectrogram displays are universal and familiar now, in every audio device and audio program. Before 1970 spectrograms were solely found in scientific and industrial situations, and required a huge amount of computing and plotting power. A realtime spectrum display was unique in 1954.
Polistra's Mill 