Theory & harmony
Circle of fifths
The circle of fifths is a diagram arranging the twelve keys by ascending perfect fifths, so each step clockwise adds one sharp and each step counter-clockwise adds one flat.
Starting at C major with no sharps or flats and moving up a fifth gives G major with one sharp, then D with two, A with three, and so on. Moving down a fifth instead gives F with one flat, B flat with two, and onward. The two directions meet at the bottom in the enharmonic keys, F sharp major and G flat major are the same pitches spelled differently.
Beyond memorising key signatures, the circle explains harmonic motion. Chord progressions overwhelmingly move by descending fifths, so a piece travelling from D minor to G to C is simply walking the circle. Relative minors sit inside the circle, a minor third below each major key, sharing its signature.
Related terms
Every term in this glossary is taught in context somewhere in Arco's curricula, on the staff, on the keyboard, and on your own fingerboard at the same time.