Pocket-sized but surprisingly deep, this DIY synth turns a tiny desktop format into a very playable virtual analog instrument. The O.P.L.A is a 4-voice polyphonic digital synth built around an ESP32 development board and Audio Kit, designed for hands-on sound design rather than menu diving.
Each voice offers three virtual analog oscillators with detuning, plus a digital multimode filter with 12dB/oct and 24dB/oct slopes. You also get three envelopes, two LFOs, and built-in wavefolding, giving it plenty of range for classic subtractive tones, bright digital textures, and evolving patches.
One of its biggest attractions is the waveform library: 4,000 Adventure Kid single-cycle waveforms are available for oscillator use. A touch-screen interface with virtual sliders and a waveform display makes browsing and tweaking fast, while the compact DIY format keeps it approachable for builders who want a small synth with a big palette.
