I have such app for more than 4 years. Your algorithm is not new - it is new for you only :) Here is the app: https://play.google.com/store/apps/details?id=com.bialamusic...

https://apps.apple.com/us/app/chord-detector/id1495811175

And this is a tuner using same algorithm: https://apps.apple.com/us/app/resonance-chromatic-tuner/id16...

Also very old stuff :)

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