Find the Key of C7 F7 G7 (12-Bar Blues)
Score the twelve major and twelve minor keys against a list of chord symbols and show the best five.
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About this tool
This page opens the chord key finder already filled in with the three chords that make up a standard 12-bar blues in C: C7, F7 and G7. The tool evaluates every major and minor key against them on load and ranks the closest matches with scale-degree labels, computed live rather than pre-rendered.
A 12-bar blues builds its entire form from the I, IV and V chords of the key, but unlike a straight pop progression it plays all three as dominant seventh chords instead of the plain major triads a strict major scale would produce — C7 on the tonic, F7 on the fourth degree and G7 on the fifth. That borrowed dominant-seventh color on every chord is the harmonic fingerprint of blues, and it is also what gives blues, rock 'n' roll and early rock their gritty, unresolved-sounding pull back to the tonic.
Transpose all three chords by the same interval to analyze a 12-bar blues in a different key (for example A7 D7 E7 for blues in A), or replace them with the chords from an actual song to check whether it follows the same I7-IV7-V7 skeleton.
Example. C Am F G ranks 1. C major - 96%, with C as I tonic, Am as vi submediant, F as IV subdominant, and G as V dominant. A minor is second at 88%. In G major, F is marked outside key.
Limit. Only major and natural minor are scored, and only the top five are shown. The page reads chord symbols. It does not detect a key from audio.