Chord Listener

Each frame of audio is transformed and its spectral peaks found. Notes are estimated by summing the harmonics above every plausible fundamental, taking the strongest, cancelling its partials and looking again, so the upper partials of one note are not heard as notes of their own. Notes from C2 to C7 are heard. A note standing exactly on a harmonic of a lower one, an octave and a fifth or two octaves above it, shares its partials and can go unheard.

A note that stops sounding is held for the arpeggio memory, so notes played one after another gather into one chord; a pause or a new chord struck together lets them go. The held notes are named by the crate's Chord, as the Chord Inspector names them.

The microphone is heard with echo cancellation, noise suppression and gain control switched off, and nothing leaves the browser.