Harmony Lab
For guitar, keys and bass · macOS · Windows · Browser

Music theory that
keeps up with
your hands.

Harmony Lab listens to what you play, or to the song you put on, and shows the key, the chords and the moves between them on your instrument as they happen. Loops caught after the fact. Lessons passed on the instrument, not with a mouse. A library that becomes your repertoire, and a music stand that takes it to the gig.

Free, forever, for the listening, every instrument view and the first tier of lessons. No account needed. Early access is by invitation while v1 is finished: say what you play and a build follows.

It listens live Your mic, your interface, or whatever is playing. Not only files. Key, chords, beat and sections arrive as the music does, and the analysis never leaves your machine.
It catches what you just played The looper is always listening. Play first. If it was good, press Loop that and the last bars are already recorded, with their chords named.
It grades what you play Every lesson is passed on the instrument. A MIDI keyboard or a guitar through an interface, stepped through from a pedal. Never a multiple-choice button.

The Play screen: Misty on the stand, the key pinned, the tempo detected, and the last bars you played already caught as a loop, open in the editor below with its chords named.

01 — Loop thatNever lose the idea you just played.

Play first.
Decide afterwards.

The looper is always listening, so there is nothing to arm. Play something, and if it was good, press Loop that: the last bars you played are already recorded, trimmed to the beat, with their chords named. Overdub on it, undo a layer, and when it has become a section, promote it onto the chart. MIDI or audio, from a keyboard or a mic.

The best take is usually the one before you pressed record.

02 — PractiseDrawn where your hands already are.

Practise with the harmony
in front of you.

The instrument shows the key as the ground, the chord of the moment on top, and the tones the next chord brings in already outlined, so a change is something you lean into. Drag across four bars to drill them with the tempo climbing each pass. Slow a recording without changing its pitch, or shift it into your key.

Guitar · board
E♭ major ⇆ E♭ minor · equator 11
11 E A D G B E 6 7 8 9 10 11 12 13 14 15 16 17 18 R 3 5 R 5 R 5 ♭7 R ♭3 ♭7 ♭3 5 R 3 3 ♭7 ♭3 5 R 5

Chord tones — every note of the sounding chord, wherever it falls under your hand.

RingedThe root of the key
SplitBoth hands share this note
NumberedScale degree, not note name
The equatorWhere major becomes minor
03 — LearnThirty lessons on a rising helix.

Theory you complete
on your instrument.

Five strands, four rising levels, thirty lessons, every one passed by playing it on a MIDI keyboard or a guitar through an interface. A placement test drops you in at the right rung. Flashcards and ear drills come back on a spaced schedule. A lesson you abandon halfway earns nothing. On purpose.

TIER 1TIER 2 TIER 3TIER 4 FoundationsColor & Function Putting It TogetherAdvanced
Interval size & the pillars Intervals · Tier 1
IntervalsChords ScalesProgressions Ear
01FoundationsFree9 lessons

Interval size, your first triads, the major and natural-minor scales, and the chords they generate. The first rung of all five strands.

02Color & FunctionPro9 lessons

Quality and motion. The dominant 7th and the restless tritone, altered triads, the minor-scale colours, cadences, and what each chord is doing in the key.

03Putting It TogetherPro7 lessons

Real harmony in play. The seventh-chord family and its inversions, pentatonics and blues, ii–V–I, and the pop axis.

04AdvancedPro5 lessons

The far reaches. Extensions and alterations, the modes, secondary dominants, and hearing function without looking.

04 — ExploreThe theory behind the chart, one click away.

Why this chord works,
and what else would.

Every chord on a chart can explain itself. Right-click one for a palette of alternatives grouped by why each works: an extension, a substitute, an inversion, a secondary dominant, a borrowed chord, a tritone sub. Ask Explore how to get from one key to another and it names the routes a teacher would, each with its reason, and traces them on the circle of fifths so you can hear the move.

Explore: the circle of fifths with the song's key family lit, and the routes from C to E♭ ranked on the right, each as a chord sequence with the reason it works.

05 — RepertoireSave it. Play from it.

Your songs, saved.
Then played from.

Every chart you write, import or capture lands in the library, tagged and starred, with when you last played it and how long you have practised it. Open one and the band plays it: click, count-in and backing band, at your tempo, in your key, with a capo if you want one. Build a setlist for Friday, print the stage sheet, and Perform walks it song by song in big type from a pedal, the next song already named.

Bring in what you haveImport iReal Pro and MusicXML files, plain chord sheets by the folder, or a photo of a page. Or start with the 349 public-domain standards in the box, melody, chords and lyrics included.
Get it back outPrint any chart, a lead sheet or a booklet with a table of contents. Export MusicXML, Guitar Pro tab, iReal, MIDI and WAV.

The Library: five saved charts, tagged and starred, each with when it was last played and how long it has been practised.

Perform mode: song 1 of 5 in Friday's set, the count-in and the stage note in the header, the next song already named, the whole thing driven from a pedal.

06 — ReadingThe same song, the way you read it.

Everyone reads music
differently.

Some people read a chord grid. Some read a lead sheet with the words under it. Some want the staff, in a Real Book hand or a classic engraving. Some want the chords flowing toward them on Horizon, or lit on the neck and the keys. Harmony Lab draws the same song every one of those ways and switches between them mid-song, in Roman numerals or Nashville numbers if you prefer. Tab is next.

Horizon E♭ major · bar 1 of 8 · 46 px / beat
1
2
3
4
5
6
7
Bbm7
Eb7
4fr
Abm7
4fr
Db7
Ebmaj7
Cm7
Fm7
Bb7
Ebmaj7
Imaj7
Bbm7
v
Eb7
I7
Abmaj7
IVmaj7
Abm7
iv
Db7
bVII7
Ebmaj7
Imaj7
Cm7
vi
Fm7
ii
NOW▲ Bbm7 · in 4 beats
Guitar
Keyboard
Notation
sounding now home · tonic away · pre-dominant pulling home · dominant borrowed · no claim made
07 — Why we build itLess friction. More understanding.

Built for musicians,
not instead of them.

Harmony Lab exists to make music theory something you understand in your hands, with as little in the way as possible. The analysis runs on your own machine. Your audio never leaves it, is never uploaded, and is never used to train anything. The app never writes a note for you: it listens, explains and follows, and the playing stays yours.

On your deviceResampling, the transform, chord and key inference: all of it runs locally, in the app you launched. No server in the loop, and nothing matched against a catalogue.
Never training dataNo recording, live input or microphone stream is stored or sent anywhere, so none of it can train a model. Usage data is about the app, not about you, and switches off in Settings in one click.
Your own AI, if you want oneThe co-writer and the built-in MCP server bring your Claude to the chart that is open. It proposes. You decide, and you play.
A scene, not a substituteWe are building for players who want to understand more and play more, together: theory made plain and put in everyone's hands, to improve the scene rather than replace the people in it.

Understand what you play. Play what you understand.

08 — PricingFree where it should be.

The listening is free.
Forever.

Hearing the key and the chords, every instrument view, the Explore map and the first tier of lessons cost nothing, on unlimited songs, with no account. Pro pays for the depth: the practice transforms, the rest of the curriculum, setlists and Perform, import and export, and sync across your machines.

Free
Free forever · no account

Everything that listens, everything that draws.

  • Live key, chord, beat and section detection, on unlimited songs
  • Every source: mic, interface, system audio, file and YouTube
  • Guitar, bass, keyboard, ukulele and notation views, the tuner, Roman and Nashville lenses
  • Charts with sections, transpose and capo, click and count-in, section loop, backing band, lyrics
  • Explore: the circle of fifths, the function map and the tree
  • Unlimited local library, and the MCP server driven by your own Claude
  • Learn tier 1: 9 of the 30 lessons, and the ear drills
  • MIDI and single-chart PDF export · 15 co-writer turns a month
Open in browser
Pro
$9 a month · $79 a year · $199 once

One licence, every surface: web, Mac and Windows. Never per platform.

  • Slow a recording down without changing its pitch, or shift its key
  • Drill any bar range, with the tempo ramp and key cycling
  • Setlists, Perform mode, stage sheets, booklets and printing
  • Learn tiers 2 to 4: the other 21 lessons, streaks, history and the spiral
  • The looper and Loop that, and the co-writer on every screen: 75 turns a month, or your own key
  • The reharmonisation palette and the modulation routes
  • Import: iReal Pro, MusicXML, bulk folders, a photo of a chart
  • Export and interop: MusicXML, Guitar Pro, iReal, WAV, Ableton Link and live MIDI out
  • Cloud sync across your machines
Get early access

Pro opens with v1, with a 14-day trial and no card. It unlocks features, never your own work: stop paying and the app drops back to Free rather than locking, and every song you made stays openable and exportable forever.

Ready when you are

Bring a song you are still learning.

Play it, drill the bars that trip you, ask why the bridge works, and put it on Friday's setlist. Early access is by invitation while v1 is finished: request one, say what you play, and a build follows.

MACOS 12+ · WINDOWS 10+ · CHROME, EDGE, SAFARI