Scales and the Circle of Fifths

A scale is the set of notes a piece of music is built from, played in order from one note up to the same note an octave higher. The first note is the tonic, the home note that gives the key its name.

The major scale

The C major scale uses only white keys: C D E F G A B C. Look at the steps between them. Most are whole steps, but E to F and B to C are half steps. That gives the pattern of every major scale:

whole · whole · half · whole · whole · whole · half

Why keys need sharps and flats

Start a scale on G and play only white keys, and the pattern breaks near the top: E to F is a half step where the pattern wants a whole step. Raise F to F♯ and the pattern is right again. That’s why G major has one sharp, F♯, in its key signature.

Start on F and the fourth note needs to come down: B♭. So F major has one flat.

The natural minor scale

Play the white keys from A to A: A B C D E F G A. This is the A minor scale. It uses the same notes as C major, starting from a different home note, so the half steps fall in different places (between notes 2 and 3, and 5 and 6). That gives minor keys their darker sound. A minor is the relative minor of C major, which is why they share a key signature. (Minor keys have two other common forms of the scale as well, which raise some of the upper notes.)

The circle of fifths

Count five notes up from C (C D E F G) and you reach G, the key with one sharp. Five up from G is D, with two sharps. Keep going and each new key adds one sharp. Going the other way, five notes down from C is F, with one flat, then B♭ with two, and so on. Arranged in a circle, all twelve keys fit around it like the hours of a clock: the circle of fifths.

At the bottom of the circle the sharp keys and flat keys meet. F♯ major (six sharps) and G♭ major (six flats) use exactly the same keys on the piano, written two ways. So do B and C♭, and D♭ and C♯. The minor keys inside the circle are the relative minors of the major keys beside them.