Not a chart — an instrument. Tap any key to hear it. Each step clockwise adds one sharp; each step the other way adds a flat. The inner ring is each key’s relative minor.
Tip: move one step clockwise (e.g. C → G) and notice a single sharp appears. That one-sharp-at-a-time pattern is the whole point of the circle.
The seven chords of C major — tap to hear each
The two keys either side of your selection (its IV and V) and its relative minor are tinted — those are its closely related keys, differing by just one sharp or flat. Music modulates to neighbours like these most easily.
Each neighbour shares all but one note. The pivot chord belongs to both keys — land on it, then a ii–V–I cadence settles you into the new key. Tap one to hear the move.
Secondary dominants — spotlight any chord with its own V7
A secondary dominant is the dominant 7th of a chord other than the tonic. Its root sits one step clockwise on the circle from its target — D7 (V7/V) points straight at G. Tap to hear it resolve.