Circle of fifths
Arrangement of keys a fifth apart with increasing accidentals.
What it means
The circle of fifths is the arrangement of the twelve major and minor keys at intervals of fifths. If one begins at C major with no accidentals and goes clockwise by a fifth upward each time, the result is G major (one sharp), D major (two sharps) and so on up to F sharp major with six sharps. Going anticlockwise by a fifth downward gives F major (one flat), B flat major (two flats) up to G flat major with six flats.
In the circle F sharp major and G flat major meet, which sound the same enharmonically. Inside lie the relative minor keys; A minor belongs to C major.
Musical use
The circle of fifths helps to determine key signatures, compare keys and plan modulations: keys that lie next to each other in the circle are closely related. It also shows the most common chord progressions, since many cadences, for instance in jazz and baroque music, follow fifths downward. Early presentations are found in Nikolai Diletsky (1679) and Johann David Heinichen (1728).
The circle of fifths should be distinguished from the mere fifth between two notes and from the falling fifth as a chord movement; it is the scheme that brings all keys into one system.
Performance practice
Learn the circle of fifths by heart, for it makes it easier for you to read key signatures and to transpose. Practise scales and chords in sequence of fifths to anchor the keys in your hand and ear.