A builder called ericCycles has constructed a functional two-antenna Theremin using a single ESP32 microcontroller and almost no supporting circuitry.
The ESP32's built-in capacitive touch inputs detect hand proximity to each antenna. One antenna controls pitch, the other controls volume. The microcontroller synthesizes the waveform internally and outputs audio through its onboard DAC directly to external speakers. No dedicated oscillator circuits, no analog tuning networks.
The full build is documented on Instructables. The original article also links a 2024 variant that replaces capacitive sensing with time-of-flight sensors, which is worth comparing if you care about how the sensing method changes playability and range.
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