Mirko Pavleski built a working audio spectrum analyzer using an ESP32, a CrowPanel 3.5 inch 480x320 touch screen LCD, and a handful of passive components. The analog audio signal is conditioned by those passives and fed directly into one of the ESP32's ADC pins. No dedicated DSP hardware. No exotic parts.
The CrowPanel 3.5 is the specific board used here, but Pavleski makes clear it is not a requirement. Any compatible display will work, with the only cost being code adjustments for different hardware. That portability is the real story: the ESP32 alone is doing the FFT and driving the display, proving how much compute headroom modern microcontrollers have left unused in typical maker projects.
Read the full project page on Hackaday.io for the schematic, source code, and component list. The signal conditioning circuit for the ADC input is worth studying closely, since getting clean audio into a microcontroller ADC without aliasing or clipping is where most similar projects quietly fail.
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