Uke Improv

Find the key from a chord chart

Paste the chart with or without lyrics. Slash chords (D/F#) and sevenths are recognized.

Find the key from a chord chart

A song's key is the chord where it comes to rest, and its chords almost always come from the same key. Knowing the key tells you which scale to improvise with and which chords to expect next.

How to use it: paste the chord chart as it appears on chord sites, with or without lyrics. The analyzer reads only the chord lines and ignores the rest. If the chart marks bars with slashes (| Dm7 G7 | C |), it uses that split; without them, it counts one chord per bar. It accepts common spellings such as Cmaj7, C7M, Bm7b5 and slash chords (D/F#).

How it decides: it tests all 24 keys, major and minor, and counts how many chords fit each one. Diatonic chords count fully; secondary dominants (like E7 before Am) and chords borrowed from the parallel key (like Fm in C major) count partially. Then it gives extra weight to the tonic at the start, at the end and repeated through the song, and to V → I cadences. When two readings tie, like C major and A minor, which use the same chords, it shows both and you choose.

The result: the key, the suggested scale for improvising (with the reason, such as blues for I7–IV7–V7 or Mixolydian when a bVII appears), the role of each chord and the share of the song the key explains. One button sends the progression to the Jam tab, where it plays as a backing track at any tempo, so you can practice improvising over the real song.

Everything runs in your browser; the pasted chart never leaves your device.

Open source (MIT) · GitHub