Adafruit Perfect Pitch Machine. Maybe the badge will have an A-400Hz tone generator in addition to tuner. When I'm tuning a guitar, I like to hear an A-440 first, to know what it should sound like.
Adafruit Kaleidoscope Eyes. NeoPixel LED ring rotating effect code samples in Arduino C and Circuit Python. One of these rings could be the entire UI output, changing its spin direction, speed, and color depending on whether the incoming tone is high, low, etc. Here's a sound reactive neopixel ring project which is very on-point, implementing a light-organ effect with the ring.
Back-of-a-napkin drawings and ideas.
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