ChordGravityYou don't pick a chord. It pulls you.
In C major, every chord tugs at the next one. Play one: the blue rings show where the harmony wants to go, and how strongly. Change key whenever you like — the progression is stored as scale degrees, so it transposes itself.
Bach — chorales · c. 1730 · Four-part chorales. The harmony still taught today.
433 pieces, 10,796 chord moves counted in major.
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All twenty-four keys, sevenths, secondary dominants and borrowed chords, playback in four styles, suggestions and cadence recognition.
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MIDI and MusicXML, with tempo, note lengths and voice leading preserved, ready for your sequencer or notation editor. Exports are unlocked in this demo so you can judge their quality.
These percentages are not rules. Nobody decided them: they were counted. Five repertoires were gone through chord by chord, and the figure shown says only how often one degree is followed by another in those composers. Nothing obliges you to follow the slope — knowing you are leaving it beats believing there isn't one. A degree only shows a figure past twenty occurrences; below that, the app tells you so instead of inventing one.
Comparing repertoires is where this gets interesting. Rock and Bach agree about the perfect cadence: V→I is worth 62% in one, 67% in the other. Everything else divides them. IV→I reaches 68% in rock against 27% in Bach: where the chorale uses the subdominant as a run-up to the dominant, the song makes it a round trip that needs nothing further. And ♭VII→I, at 57% in rock, simply does not occur in Bach. Pick a chord, then change repertoire in the menu and watch the pull lines redraw.
What these figures cannot tell you. They ignore harmonic rhythm, position in the phrase, melody and inversion — everything that makes the same chord move sound ordinary or startling. An uncommon chord is not a wrong chord; often the reverse. The samples are also uneven — 433 chorales and 200 songs against 25 quartet movements — and some repertoires are poorly served by a grid of scale degrees, Palestrina above all, whose polyphony is modal and predates the tonal system. Minor is switched off for the quartets, which barely contain any in this sample.
No jazz yet. The available collections of standards note a single key for a whole tune, whereas jazz changes key by the bar. Figures drawn from that would look right without being right, which is worse than showing nothing.
The sound and the writing. Two oscillators per voice, synthesised in the browser and deliberately plain: the point is to hear function, not timbre. The voice leading keeps common tones from one chord to the next and moves the rest by the shortest path. The MIDI export writes block chords rather than the playing style, so that it stays raw material.
Sources. The four early repertoires are analysed from the music21 corpus (MIT). The rock corpus comes from Trevor de Clercq and David Temperley's analysis, obtained through ChoCo, a Polifonia project, under CC BY 4.0 — there, the degrees and keys are written by musicologists rather than inferred by machine.