Eidolon is a hybrid synthesizer plugin in real-time C++ on JUCE, built over an eight-week independent learning contract at The Evergreen State College (Summer 2026, 12 credits). One source tree builds VST3, AU, CLAP and a standalone app, and version 0.1.0 is a universal macOS download.

The voice. Up to twelve voices, six by default, each with three oscillator slots. A slot can be a Bézier subtractive oscillator band-limited with minBLEP, an additive oscillator summing up to thirty-two partials under a movable window, or a mipmapped wavetable, with FM and ring modulation between them. The signal then passes two wavefolders with four topologies (Buchla, Serge with a Lockhart variant, Bent and WaveMult), two Zavalishin TPT state-variable filters in series with five Character modes, and an amplifier modelled as a CA3080 into a Pines diode stage, all at four times the host rate. Four envelopes and eight LFOs feed a 24-slot modulation matrix routing twelve sources to twenty targets.

Character. The analog behaviour is many small mechanisms placed where they act in a circuit, each switchable and measurable on its own, with no machine learning. Per-voice offsets drawn from a fixed seed give the voices the spread of a Prophet-5 while every render stays reproducible. The output runs through a model of the Soundcraft 600 line path staged in volts, followed by an effects rack, off by default: a 12AX7 tube cascade, bucket-brigade delay, Dattorro plate and Jiles-Atherton tape. A change that alters the sound is accepted only after a level-matched listening comparison.

The evidence. Five pieces of music, each written to play one capability: the filter, the additive window, the effects rack, the wavetable scan and the modulation matrix. Five of the contract's six rows were met; the sixth, automation over OSC, was scheduled after the contract closed and was not undertaken.