Find the chords in a song from an audio file

Unveil's Chord Transcription tool listens to an uploaded track and returns its key, scale, tempo, time signature and a timestamped list of chords. It also writes the core progression in Roman numerals. You need a free Unveil account to run it, and signed-out visitors are sent to sign-up.

How chord detection works

A chord is a group of notes heard together, but audio is just a single waveform. To name a chord, an analysis system has to work out which pitches are sounding at each moment, identify the bass note, and match the combination to a known chord shape such as a minor triad or a major seventh. It also has to decide where one chord ends and the next begins.

Traditional detectors convert the signal into a chroma representation, which folds all the energy onto the twelve pitch classes, and compare it with chord templates. Newer approaches use machine learning models that have learned what chords sound like in context. Unveil uses the latter: it sends the audio to Google's Gemini model with a prompt that asks for the key, scale, tempo, every chord change and the harmonic function of each chord.

What the tool returns

Key and scale, such as a major or minor key, or a mode like Dorian or Mixolydian.
BPM and time signature. If no time signature comes back, the page shows 4/4 by default.
A chord timeline: each row has a timestamp, a chord symbol such as Am, G7 or Cmaj7, a harmonic function label such as tonic, subdominant, dominant or borrowed, and how long the chord lasts.
The core progression in Roman numerals, for example i - VI - III - VII, which lets you compare songs regardless of key.
A complexity rating: simple means one to four diatonic chords, moderate means five to seven chords with some extensions, and complex means many chords with chromatic or jazz voicings.

Preparing your audio

Chord detection works best when harmony is clearly audible. Use a full-quality file rather than a low-bitrate copy, and prefer a version with the harmonic instruments (guitar, piano, pads, bass) well forward in the mix. Tracks that are mostly drums, spoken word or a single unaccompanied vocal give the model very little harmony to read.

Shorter, focused clips are easier to check. If you want the chords of one section, trim the file to that section before uploading, so timestamps start at zero and you can compare them to your own session quickly.

Using the tool

Create a free Unveil account or sign in. Signed-out visitors are sent to sign-up.
Open Chord Transcription and drop in an audio file or click to browse.
Wait while the file uploads and the harmony is analyzed.
Read the key, BPM, time signature and complexity cards at the top.
Scroll the chord timeline and use the Copy button to paste the timestamps and chord names into your notes or chart.
Use the Roman numeral progression and the three suggestions as starting points for your own arrangement or remix.

Limits and honest caveats

Chord naming is partly subjective. The same notes can be written as Am7 or C6, and a bass note change can be a slash chord or a new chord entirely. Two experienced musicians will often disagree on a few chords in any song, so an automatic result will too.

Extended and altered chords (9ths, 11ths, 13ths, sus chords) are the most likely to be simplified or misnamed.
Fast harmonic rhythm, where chords change every beat, makes timestamps less exact.
Tracks with detuned instruments, heavy distortion or very dense layering blur the pitch information.
Tempo and key can be off on material with tempo changes or modulations.
The output comes from an AI model, so a result can differ if you run the same file again.

How to check and use the result

Always verify by ear. Play the chord timeline on a piano or guitar while the original track plays, and fix anything that sounds wrong. Pay attention to the first and last chords, which usually reveal the key, and to the chorus, which tends to be the most repeated and easiest to confirm.

The Roman numeral progression is the most useful part for songwriting. Because it is key independent, you can transpose it to any key, swap one chord for a related one to change the mood, or compare it with progressions from songs you know. A frequent mistake is to copy an exact chord sequence into a release without considering that the harmony, melody and arrangement are all separate things worth making your own.

What you get

Key, scale, BPM, time signature and a complexity rating of simple, moderate or complex.
A chord timeline with a start time, chord name, duration and harmonic function for every change.
The core repeating progression in Roman numeral notation, a list of unique chords and a short mood description.
Three suggestions for remixing or building on the progression, plus a copy button for the timeline.

Questions

How does the chord finder analyze my song?

Your audio is uploaded and analyzed by Google's Gemini AI model using a music theory prompt. It returns structured data for the key, tempo, chord events and progression, and Unveil displays it as a timeline.

Which audio files are accepted?

The upload box accepts audio files and lists MP3, WAV, FLAC, M4A and AIFF. Unveil does not state a file size limit on this page.

Will the chords always be correct?

No. The model is asked to pick the most likely chord when something is ambiguous, so treat the output as a strong first draft and check it against the recording by ear or on an instrument.

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