Key signatures chart

Overview

With any note as a starting point, a certain series of intervals produces a major scale: whole step, whole, half, whole, whole, whole, half.

Starting on C, this yields C-D-E-F-G-A-B-C (a C-major scale). There are no sharps or flats in this scale, so the key signature for C has no sharps or flats in it. Starting on any other note requires that at least one of these notes be changed (raised or lowered) to preserve the major scale pattern. These raised or lowered notes form the key signature. Starting the pattern on D, for example, yields D-E-F♯-G-A-B-C♯-D, so the key signature for D major has two sharps—F♯ and C♯.

Key signatures indicate that this applies to the section of music that follows, showing the reader which key the music is in, and making it unnecessary to apply accidentals to individual notes.

In standard music notation, the order in which sharps or flats appear in key signatures is uniform, following the circle of fifths: F♯, C♯, G♯, D♯, A♯, E♯, B♯, and B♭, E♭, A♭, D♭, G♭, C♭, F♭. Musicians can identify the key by the number of sharps or flats shown, since they always appear in the same order. A key signature with one sharp must show F-sharp, which indicates G major or E minor.

There can be exceptions to this, especially in 20th-century music, if a piece uses an unorthodox or synthetic scale and an invented key signature to reflect that. This may consist of sharps or flats that are not in the usual order, or of sharps combined with flats (e.g., F♯ and B♭). Key signatures of this kind can be found in the music of Béla Bartók, for example.

In a score, transposing instruments will show a different key signature to reflect their transposition but their music is in the same concert key as the other instruments. Percussion instruments with indeterminate pitch will not show a key signature, and timpani parts are sometimes written without a key signature (early timpani parts were sometimes notated with the high drum as "C" and the low drum a fourth lower as "G", with actual pitches indicated at the beginning of the music, e.g., "timpani in D–A"). In polytonal music, where different parts are actually in different keys sounding together, instruments may be notated in different keys.

Conventions

The order in which sharps or flats appear in key signatures is illustrated in the diagram of the circle of fifths. Starting the major scale pattern (whole step, whole, half, whole, whole, whole, half) on C requires no sharps or flats. Proceeding clockwise in the diagram starts the scale a fifth higher, on G. Starting on G requires one sharp, F♯, to form a major scale. Starting another fifth higher, on D, requires F♯ and C♯. This pattern continues, raising the seventh scale degree of each successive key. As the scales become notated in flats, this is shown by eliminating one of the flats. This is strictly a function of notation—the seventh scale degree is still being raised by a semitone compared to the previous key in the sequence. Going counter-clockwise from C results in lowering the fourth scale degree with each successive key (starting on F requires a B♭ to form a major scale). Each major key has a relative minor key that shares the same key signature. The relative minor is always a minor third lower than its relative major.

The key signatures with seven flats and seven sharps are usually notated in their enharmonic equivalents. C♯ major (seven sharps) is usually written as D♭ major (five flats) and C♭ major is usually written as B major.

The key signature may be changed at any time in a piece by providing a new signature. If the new signature has no sharps or flats, a signature of naturals, as shown, is used to cancel the preceding signature. If a change in signature occurs at the start of a new line on the page, where a signature would normally appear, the new signature is customarily repeated at the end of the previous line to make the change more conspicuous.

In music theory, relative keys are the major and minor scales that have the same key signatures (enharmonically equivalent), meaning that they share all of the same notes but are arranged in a different order of whole steps and half steps. A pair of major and minor scales sharing the same key signature are said to be in a relative relationship. The relative minor of a particular major key, or the relative major of a minor key, is the key which has the same key signature but a different tonic. (This is as opposed to parallel minor or major, which shares the same tonic.)

For example, F major and D minor both have one flat in their key signature: B♭. Therefore, D minor is the relative minor of F major, and conversely F major is the relative major of D minor. The tonic of the relative minor is the sixth scale degree of the major scale, while the tonic of the relative major is the third scale degree of the minor scale. The minor key starts three semitones below its relative major; for example, A minor is three semitones below its relative, C major.

The relative relationship may be visualized through the circle of fifths.

Relative keys are a type of closely related keys, the keys between which most modulations occur, because they differ by no more than one accidental. Relative keys are the most closely related, as they share exactly the same notes.

The major key and the minor key also share the same set of chords. In every major key, the triad built on the first degree of the scale is major, the second and third are minor, the fourth and fifth are major, the sixth is minor, and the seventh is diminished. In the relative minor, the same triads pertain. Because of this, it can occasionally be difficult to determine whether a particular piece of music is in a major key or its relative minor.