The key and chords of a song, bar by bar
For playing and arranging by ear. The sheet and the melody are only a rough aid.
Drop a song here
Audio, video or MIDI
Often wrong. Use it as a hint.
MusicXML opens in MuseScore and most notation programs. MIDI opens in any music app.
About and privacy
What it does
ArrangingCompanion is mainly for the key and the chords of a song, bar by bar. It finds the key, the tempo, the meter and a chord for every bar, and shows them as a chord chart and as a rough sheet that follows the music. An uncertain chord gets a second choice, like (G?). A MIDI file gives exact notes and bars.
What it does not do
It does not write an exact transcription or an arrangement. It does not separate instruments. The melody is experimental and often wrong. The meter can be wrong, mostly in freely played music. It cannot open copy-protected files.
Privacy
Your files stay on your device. Nothing you open is uploaded. The first song downloads the analysis program and models, about 50 to 65 MB, once. This browser keeps them, so later songs work offline too. The page sets no cookies. Besides its own files, it stores only the melody box setting.
Visits are counted with Cloudflare Web Analytics. It sets no cookies and does not see your files.
Credits and licenses
- Beats: Beat This! by the Institute of Computational Perception, JKU Linz (MIT license).
- Chords: BTC, the bi-directional transformer for chord recognition by Jonggwon Park and others (MIT license).
- Experimental melody: Basic Pitch by Spotify (Apache License 2.0).
- Running the models: ONNX Runtime Web by Microsoft (MIT license).
- Drawing the sheet: Verovio by RISM Digital (LGPL 3.0), included as its own unmodified file.
- Fonts: Libre Baskerville and PT Serif (SIL Open Font License); music signs from Noto Music (SIL Open Font License). Icons: Material Symbols (Apache License 2.0).