Chord Lab — Chord Progression Studio
Build chord progressions from ranked suggestions that explain themselves, shape voicings, rhythm and individual notes in a piano roll, and export MIDI. Out-of-key chords are read as borrowed chords, secondary dominants or modulations.
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. The left-hand bass and right-hand voicing are chosen to connect smoothly to the chords on either side, and genre comping patterns, swing, humanize and sustain pedal come along with them.
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.