Drop in a recording. The key comes back with the chords that decided it.
Listening…
That is your free songs for today.
The app has no daily limit — and it keeps the chords with the song, puts them over the words, and lets other people play on it.
Key, estimated
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Progression
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A key is the set of chords a song keeps coming home to. The tool listens for the chords first, then asks which key holds most of them and which one the song rests on. That is why the answer above says estimated: it is the same judgement a player makes by ear, made from the same evidence, and a song that borrows a chord from next door can fool either of you for a bar.
G major and E minor share every chord. What separates them is where the song feels finished. If the last chord of the chorus sounds like a door closing on G, it is in G; if it settles on Em and stays there, it is in E minor. The tool reports the one the recording leans on. When it gets the pair right and the home wrong, the chords are still right, and you will hear which of the two it is in about four bars.
Every key has seven chords that belong to it. Once you know the key, the ones the song has not used are the ones worth trying next, and a capo that puts it in your voice is a matter of counting. The app does that arithmetic on your own recordings and keeps the sheet with the song.
Not a list of seven chords: the three you haven't used →