Function render_phrase 

pub fn render_phrase(
    tree: &PatchTree,
    spec: &PhraseSpec,
) -> Result<RenderedPhrase, PatchError>

Compile tree and render it playing the phrase.

Chord notes (crate::phrase::Note::chord) are rendered by additional compiled voices summed into the same buffer with no attenuation: two voices sounding at once being louder and denser than one is exactly the polyphonic-stacking information the stimulus exists to capture, whole- phrase loudness is normalized downstream, and the vet ceiling scales with crate::phrase::PhraseSpec::max_voices. Chord voices tick from their note’s onset (cold start, like live voice allocation), share the note’s gate, and after release keep ticking until their output parks on silence so a long tail is never truncated into a click. Tick order per sample is fixed (main voice, then chord voices in pitch order), which keeps the thread-local RNG draw sequence — and therefore the render — deterministic.