MIDI Piano & Guitar Chords

FreeMIDIChords is a free, open-source music theory tool suite that works with any MIDI keyboard. Connect a controller and the app detects chords and intervals in real time, displaying them on staff notation, a piano keyboard, and an interactive circle of fifths. It also generates chords on demand, plays them back through MIDI or built-in audio, and includes scales, and a metronome. Available as a web app (with Web MIDI API support), iOS/Android app, and desktop app for Mac and Windows — with no subscriptions, no accounts, and no paywalls.

FreeMIDIChords innovates by making MIDI-powered music theory accessible without cost or setup barriers. Most theory tools are either expensive, require software installation, or lack MIDI integration. FreeMIDIChords combines real-time MIDI input detection, chord generation with MIDI output, and rich visualization — staff notation, piano keyboard, and circle of fifths — in a single free tool that runs in the browser via the Web MIDI API, requiring no installation.

Its bidirectional MIDI approach is distinctive: the same app listens to what you play and identifies it, or takes a chord you select and performs it — turning a MIDI keyboard into both input and output for music theory exploration.

The cross-platform reach (web, iOS, Android, desktop) through a unified feature set also sets it apart, ensuring musicians can learn and practice on any device, with or without a MIDI controller.

A self-taught musician sits at a secondhand keyboard with no music teacher and no budget for software. They play a chord they heard in a song — and FreeMIDIChords instantly names it, shows it on the staff, and places it on the circle of fifths. They move to the next chord, and the next, and slowly the song they’ve been trying to learn reveals its harmonic structure.

This is the use case FreeMIDIChords was built for: removing the wall between curiosity and understanding. Music theory has historically been taught in classrooms or through expensive software. FreeMIDIChords puts that knowledge directly in the hands of anyone with a MIDI keyboard and a browser — no teacher, no subscription, no barrier.