Chord Lab — Chord Progression Studio

What is Chord Lab?

Composing is a chain of choices — a studio for the next chord

Chord Lab is a studio for building chord progressions by hand. Pick an empty slot and it ranks the chords that fit there in context — but the ranking is not the point, the "why" is. Every candidate carries a one-line reason: ii to V moves from leaving to tension; a V–I at the end of a phrase is the full stop at the end of a sentence. It is not a tool that hands you the right answer; it is a tool that plays each option and tells you what makes it sound the way it does.

You are never restricted to the suggestions. Play a chord from outside the key and nothing blocks you — it gets interpreted instead. A badge shows the most plausible reading (a chord borrowed for a moment, a secondary dominant aimed at what comes next, or a real modulation), and you can declare the reading you meant. Declare a modulation and the roman numerals and every later suggestion re-key from that point on.

Playback uses a grand piano sampled at several dynamic levels, through a reverb and a master limiter. Genre comping patterns, swing, humanize and sustain pedal come along with it.

Auto voicing — choose the chord, we place the notes

Choosing a chord and playing it well are two different jobs. The same chord sounds completely different depending on how many notes you play, which octave each one sits in and how far apart they are spread — very nearly the whole difference between an amateur and a professional playing the same symbol. In Chord Lab that part is not your problem. Choose the chord and the left-hand bass and right-hand harmony are placed for you.

The rules are the ones pianists actually use. From sevenths up, the bass has already stated the root, so the right hand drops it and keeps the 3rd and 7th — the notes that give a chord its face. The hands stay an octave to a tenth apart so the low end never clumps, and spacing widens the lower it goes. When the chord changes, notes the two chords share stay put and only the rest move to the nearest spot, so your hands never jump and the sound flows. Switch on a tension that would sit a half step under a chord tone and it gets lifted a ninth above instead.

It is a switch, of course. Turn “Auto voicing” off in the voicing · rhythm row and you hear the difference at once. Want to shape it yourself? The piano roll lets you edit individual notes. Curious why each rule exists? [What Is Voicing?](/blog/voicing-basics) walks through them one by one. And once the arrangement is done, download the whole thing as a MIDI file and pick it up in your DAW.

How to get the most out of it

If you are new, open 📚 Library and load a famous progression — ii–V–I, the Pachelbel canon, a 12-bar blues, the royal-road progression — then change one chord at a time. Breaking a progression you already know is the fastest way to hear why it worked.

Once the progression feels right, the piano roll lets you shape individual notes. The chord block is the source of truth, and the moment you touch the roll that block opts out of the automation so your edit is never overwritten. Bars, time signatures and sections (verse, chorus) are yours to arrange, and the meter can change mid-song.

Export the result as MIDI to keep going in a DAW — chord-name markers and pedal data are written too — or share the whole progression as a link. If you have a MIDI keyboard, connect it and the chords you play are recognized and placed on the timeline. Everything is saved in your browser; no account required.