Interactive Circle of Fifths (and Thirds)

The circle of fifths is music's map of the twelve keys, and here it is interactive: tap any key to hear it, see its key signature, its relative minor, and the seven chords it contains — played on a real guitar voice, with classic progressions (I–V–vi–IV, ii–V–I, the '50s loop) spelled out in that key, each with a play button.

The second view, the circle of thirds, shows how chords are physically built: stack alternating thirds around the wheel and watch major and minor triads draw themselves, then the symmetric diminished and augmented patterns. A transposition ring on the fifths view doubles as a capo calculator — rotate it and see what shapes to play for any sounding key.