Polyphonic Chord Synthesizer

An embedded chord synthesizer built on a Teensy 4.1. Multi-voice synthesis — waveform oscillators, envelopes, and mixers — routed through a DAC and I²S output, with edit-mode state handling and saved chord slots so a player can perform a set without touching the UI mid-song.

The interesting part wasn't the synthesis; the math of summing oscillators is textbook. The interesting part was fitting state, input handling, and timing inside the Teensy's memory budget without dropping voices. Embedded audio is cruel in a specific way: a ten-millisecond hiccup is audible. Everything in the code base is organized around the constraint that the audio callback must never allocate, never block, and never miss its deadline. Once you commit to that, most of the design decisions write themselves.