An audio file
Load a track and scrub it. Deterministic, repeatable, and the fastest way to check whether it hears what you hear.
macOS · Windows · Browser
It listens,
It listens,
and shows you
what to play next.
Harmony Lab hears music — an audio file, your microphone, or the instrument plugged into your interface — and shows the key, the chords, and the notes that will work over them, while it is still playing.
Free forever for the live analysis, the pathways and every instrument view. No account needed to play. Access is by invitation while v1 is finished — mail me and I will add you.
Analysis
22 050 Hz
One canonical rate. Every source is resampled to it before a single window is cut.
Audio uploaded
0 bytes
No recording, no live input and no microphone stream ever leaves the machine.
Songs
Unlimited
Never metered. Not on the free tier, not ever — see the pricing note.
Harmony Lab
PlaySongExploreLearnLibrary
0:00
Guitar
File Misty
Playing
Key
E♭
major
Locked · chosen, not heard
Chord
Ebmaj7
E♭ G B♭ D
bar 1 of 8
Tempo
4/4 · 1 bar in
68
bpm
TAP
CLICK
▷ COUNT ME IN
Ready no loop
Loop editor →
Controls
Misty
by
Erroll Garner
E♭ major · 68
ChordsSheetHorizonMelody
Guitar · E♭ major ⇆ E♭ minor · equator 11
Diagonal over the boxes
Major / minor
major — the track, over its box
minor — the track, over its box
ANALYSIS 22 050 HzFFT 2048HOP 512 · 23.2 msRING OK
The Play screen, running. Every colour on it means something musical — the chrome spends none.
01 — The gapWhy another chord detector is not the answer.
Most tools stop at naming the chord.
There is a long stretch between playing some chords and hearing where a song wants to go. It lasts years for most people, and the reason is that the feedback is slow: you play something, it sounds wrong, and nothing tells you why — or what to reach for instead — while your hands are still on the instrument.
Chord detectors label what is playing. That is the easy half, and it is close to free now. None of them answer the question you are actually asking: given what I just heard, what can I play, and how will it feel?
Detection without direction is a dictionary with no sentences.
02 — Guitar boardDrawn where your hands already are.
Two hands, one shape,
three frets apart.
The board is not a scale diagram with the current chord highlighted. It is a map of a key with an equator running through it: below the line the major side sits under your pinky, above it the same shape sits under your index and turns minor. Learn one shape and you have both tonalities and every position on the neck.
Every dot is computed from the scale in the key the app is hearing — not a stored fingering chart. Change key and the whole board moves.
Guitar · board
E♭ major ⇆ E♭ minor · equator 11
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 — HorizonA heads-up display for a song.
The next chord arrives
before you need it.
Reading a chart means looking ahead and losing your place. Horizon does the looking for you: the song flows right to left toward a fixed NOW line, so what is sounding is always in the same spot on screen and what is coming is already in view — with the fingering for it drawn above the lane, not two bars away on a page.
Chord blocks are coloured by what they are doing in the key, not by what they are called. A borrowed chord stays neutral rather than being forced into a function it does not have.
Horizon
E♭ major · bar 1 of 8 · 46 px / beat
sounding now
home · tonic
away · pre-dominant
pulling home · dominant
borrowed · no claim made
04 — LearnThirty lessons on a rising helix.
Theory taught in a spiral,
not a straight line.
Five subjects run side by side — intervals, chords, scales, progressions, ear — and each is revisited at four rising levels of depth rather than finished once and abandoned. You meet the major scale in your first hour and again, differently, at the top; you meet triads before seventh chords, because the second is unplayable without the first.
Every lesson is graded by what you play — on a MIDI keyboard, or a guitar into an interface — not by which button you press. A lesson you abandon halfway earns nothing: no points, no streak, on purpose.
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 diatonic chords they generate — the first rung of all five strands.
02Color & FunctionPro9 lessons
Quality and motion — the dominant 7th and altered triads with the restless tritone, the minor-scale colours, cadences, and harmonic function.
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 — chord extensions, the modes, secondary dominants, and functional listening.
Placement
A short listening and playing test drops you in at the right rung on each of the five strands. You are never made to start from the bottom of a subject you already know.
05 — On your deviceNot a hedge. An architecture.
Your audio never
leaves the room.
The analysis — resampling, the transform, chord and key inference, the pathways — happens in workers on your own machine, in the app you launched. There is no server in that loop, and no recording or live input is ever uploaded.
No uploadAudio from a file, your mic, or your system output is analysed in place and stays there.
No lookupsNothing is matched against a streaming service or a chord catalogue. The app works the harmony out itself, from sound.
No account to listenInstall it and play. Signing in is optional, and only ever links the history you already have.
Your own AI, on your machineThe app never calls a language model to do the listening. It exposes the open song over a loopback server so your Claude can read and shape it — your model, your machine.
And what does leaveTwo things, both nameable. Asking the co-writer a question sends that question and the chart it is about. Usage data — which chords and keys you worked on, never audio and never what you asked the co-writer — is on by default and switches off in Settings, permanently, in one click.
06 — SourcesAnything that makes a sound.
Three ways in.
01
02
Your mic or interface
Play a guitar, a keyboard, or sing. The analysis runs on what you are doing right now, not on a recording of it.
03
Whatever your computer plays
Capture the system output or a browser tab and improvise over it. Only the sound is analysed; the picture is discarded.
07 — PricingFree where it should be.
The listening is free.
Forever.
Hearing the key, the chords and the pathways is the whole point of the thing, and gating it would make the product worse for everyone — including the people who pay. Nothing here is ever metered by the song, the minute or the analysis.
Free
Free
forever · no account
Everything that listens, everything that draws.
- Live key, chord, beat and section detection — unlimited songs
- Safe / Color / Tension pathways, ungated
- Mic, interface, system audio, file and YouTube capture
- Every instrument view, the tuner, and the whole Explore screen
- Unlimited local library · corrections, on every tier, forever
- The MCP server, driven by your own Claude
- Learn tier 1 — 9 of the 30 lessons
- MIDI and single-chart PDF export · 15 assistant turns a month
Pro
$9
a month · $79 a year · $199 once
One licence, every surface — web, Mac and Windows. Not per platform.
- Pitch-preserving speed change, and key shift
- The looper — MIDI and audio, overdub, Keep that
- The co-writer, on every screen · 75 turns a month, or your own key
- Learn tiers 2–4 — the other 21 lessons, plus streaks and the spiral
- All import: iReal, MusicXML, Guitar Pro, bulk folder, photo of a chart
- All export and interop, Ableton Link and live MIDI out
- Setlists, Perform mode, printing and booklets
- Cloud sync across your machines
Pro opens with v1, with a 14-day trial and no card. It unlocks features, never your own work: if you stop paying the app drops to Free rather than locking, and every song you made stays openable and exportable forever.
Ready when you are
Put it on, and play something.
Point it at a song you have never worked out and see how far you get. Access is by invitation while v1 is finished — tell me what you play and I will send you in.
MACOS 12+ · WINDOWS 10+ · CHROME, EDGE, SAFARI