Here's a page that shows a real-time spectrogram of audio recorded from your microphone:
https://observablehq.com/@skybrian/microphone-audio-spectrogram
Here's a spectrogram of a chromatic ascending scale played on my melodica.
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Here are three C scales played on the treble side of my accordion, using different switches. (L, then M, then LMM.)
@tindall@cybre.space perhaps relevant to your interests?