Find the chords of a song from the audio itself. Drop an MP3 or other recording and the detector follows the harmony beat by beat, shows a colour-coded chord timeline that moves with playback, estimates the key and tempo, and builds a bar-by-bar chord chart you can transpose and download.
Last updated:
Showing a demo song.
Now–
Next–
0:00 / 0:00
More changesFewer changes
Transpose
Chord chart
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How to use the Song Chord Detector
Drop a song (MP3, M4A, WAV, OGG, FLAC or a video). A demo song is analysed when the page opens.
Wait a few seconds while the harmony and beat are analysed in your browser.
Press play and follow the Now and Next chords; click a block in the timeline or a bar in the chart to jump there.
Refine: add 7th chords if the song uses them, raise Smoothing if chords flicker, set the time signature, and transpose to your capo position or vocal key.
Download the chord chart as text or the timeline as CSV, and check it by ear on your instrument.
Chord types the detector recognises
Each chord is a template of pitch classes. The detector scores every template against the notes heard on each beat. Wider vocabularies catch more colour chords but also produce more false 7ths and sus chords, so start with major and minor.
Chord
Symbol
Intervals from the root
Example on C
Vocabulary
Major
C
1 – 3 – 5
C E G
Major and minor
Minor
Cm
1 – ♭3 – 5
C E♭ G
Major and minor
Dominant 7th
C7
1 – 3 – 5 – ♭7
C E G B♭
+ 7th chords
Major 7th
Cmaj7
1 – 3 – 5 – 7
C E G B
+ 7th chords
Minor 7th
Cm7
1 – ♭3 – 5 – ♭7
C E♭ G B♭
+ 7th chords
Diminished
Cdim
1 – ♭3 – ♭5
C E♭ G♭
+ 7ths, dim, aug, sus
Augmented
Caug
1 – 3 – ♯5
C E G♯
+ 7ths, dim, aug, sus
Suspended 4th
Csus4
1 – 4 – 5
C F G
+ 7ths, dim, aug, sus
Suspended 2nd
Csus2
1 – 2 – 5
C D G
+ 7ths, dim, aug, sus
Getting the best results
Use a clean, full-quality file. Heavily compressed audio, live recordings with crowd noise or tracks with loud effects make the harmony harder to read.
Check easily confused pairs. Relative chords share two notes: C/Am, G/Em, F/Dm. If the chart says Am where you hear C, listen to the bass note.
Slash chords and inversions are reported by their chord name only (C/E shows as C).
Use the chord progression, not the exact timing, when the song speeds up or slows down; the bar grid assumes a steady tempo.
Confirm with an instrument. Play along with the Now chord: if it clashes, try the chord that shares two of its notes.
Frequently asked questions
How does the chord detector work?
The song is mixed to mono and analysed in short overlapping windows with a Fourier transform. Each spectral peak is mapped to one of the 12 pitch classes (C, C♯, D…), giving a chroma vector that shows which notes sound. A beat tracker finds the pulse, the chroma is averaged per beat and compared with templates for every chord type (for example C major = C, E, G). A Viterbi decoder then picks the most likely sequence, with a penalty for changing chord that the Smoothing slider controls.
How accurate is it?
On clear pop, folk and rock recordings with guitar or piano, most chords are usually found, but automatic chord recognition is never perfect. Common mistakes are confusing chords that share two notes (C and Am, or Em and G), missing quick passing chords, and reading a strong melody or bass note as part of the chord. Treat the result as a first draft and check it by ear.
Why does it say a chord my song doesn't have?
Try raising Smoothing to remove short wrong chords, or switch Chord types back to major and minor: the larger vocabulary can over-fit 7ths and sus chords. If every chord is one semitone off, the recording may be tuned between standard pitches (common with older records or detuned guitars); use Transpose to correct the names.
How are the key and tempo found?
The key is estimated by correlating the song's overall note distribution with the Krumhansl–Kessler major and minor key profiles and choosing the best match. The tempo comes from the autocorrelation of an onset (note attack) envelope, and beat positions are chosen by dynamic programming. Songs with a free tempo or very quiet drums may get a half or double tempo, which only changes how the bars are grouped.
Can I use the chords with a capo?
Yes. Transpose shifts every chord name. For example, with a capo on fret 2, transpose by −2 to see the chord shapes to play: a song detected in A major then reads in G major shapes. Transposing does not change the audio, only the names.
Is my song uploaded?
No. Decoding, the Fourier analysis, beat tracking and chord recognition all run in JavaScript in your browser. The song never leaves your device.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.