OneTaskBy Tim King · Updated
Chord Detector
Find the Chords in a Song From Audio, Major, Minor and Seventh
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How the Chord Detector works
This chord detector listens to a song and writes out its chord progression with the time of every change. Drop an audio file, drag across the waveform to focus on a section, and read the chords, the most used ones and a timeline you can export as a CSV or JSON file.
How the chord detector works
The audio is cut into short steps and each one is turned into a spectrum. The energy of every note is folded into twelve pitch classes, C through B, regardless of octave. That profile is matched against major, minor, dominant seventh, major seventh and minor seventh shapes on all twelve roots, and the closest match wins. Repeated matches in a row are merged into one chord.
Choosing the chord detector analysis step
Half a second suits most pop and rock songs. Use a quarter second for fast changes, or one to two seconds for slow ballads, where a longer step averages out passing notes and melody.
Getting better results
Chord detection from mixed audio is never perfect. Bass lines, vocals and drums all add notes that are not in the chord. Select a section with a steady accompaniment, and treat the result as a starting point to check by ear with a chord player.
FAQ
Why does it show a seventh chord when the song uses a plain triad?
A melody note or bass line can add the seventh for a moment. The tool slightly favours triads, but if the seventh is loud it will appear. Check it by ear, or use a longer analysis step.
What does N mean in the export?
N means no chord: the step was silent or below the loudness threshold. These rows are kept in the CSV and JSON so the timeline has no gaps, but they are left out of the progression shown on screen.
Does the chord detector know the key?
It names chords, not keys. Run the same file through the key detector to find the key, which helps you decide whether an E♭ should really be read as D♯ in context.
See also: all Audio tools, Images, Video & Screen, PDF, SVG, Simulations & Screensavers, Generative Art, Chart Makers, 3D Model Viewers, Drawing Pads, Mockups & 3D Making, Diagram Makers, 3D Science, Tracker Music.
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