Key signature

A key signature is a set of flat or sharps and is used to notify which music notes that will be altered with flats or sharps. The key signature is always written just after the clefs.

Key signature

In the example above, the key signature indicates that all B, E and A notes will be altered in B♭, E♭ and A♭, because the three first flats in the order of flats are B♭, E♭ and A♭.

It is exactly the same as this below:

staff without key signature

Or it can contain from one to seven flats:

Key signature with seven flats

Or from one to seven sharps:

Key signature with seven sharps

The key signature can be null (no sharps or flats):

Null key signature

But a key signature can't be a mixture of sharps and flats:

Invalid key signature



You can see that the flats and the sharps are written on specific lines or space of the staff united states of america (stave united kingdom): All sharps and flats of the key signature are written like the order of flats and the order of sharps

Order of flats:
order of flats

Order of sharps:
order of sharps

Order of flats and sharps on the circle of fifths

You can find the order of flats and the order of sharps on the circle of fifths, sharps are clockwise and flats are counterclockwise:

Order of flats and sharps on the circle of fifths

Major and minor scale with null key signature

There are only two scales with null key signature:

Key signatureMajor scaleMinor scale
Null key signatureC MajorA minor

Major and minor scales with sharp key signatures

There are seven major scales and seven minor scales with sharp key signature:

Key signaturesMajor scalesMinor scales
Key signature with one sharpG MajorE minor
Key signature with two sharpsD MajorB minor
Key signature with three sharpsA MajorF sharp minor
Key signature with four sharpsE MajorC sharp minor
Key signature with five sharpsB MajorG sharp minor
Key signature with six sharpsF sharp MajorD sharp minor
Key signature with seven sharpsC sharp MajorA sharp minor

Major and minor scales with flat key signatures

There are seven major scales and seven minor scales with flat key signature:

Key signaturesMajor scalesMinor scales
Key signature with one flatF Major scaleD minor scale
Key signature with two flatsB flat Major scaleG minor scale
Key signature with three flatsE flat Major scaleC minor scale
Key signature with four flatsA flat Major scaleF minor scale
Key signature with five flatsD flat Major scaleB flat minor scale
Key signature with six flatsG flat Major scaleE flat minor scale
Key signature with seven flatsC flat Major scaleA flat minor scale

Natural key signature

Natural key signature is used to cancel previous key signature:
Natural key signature

Changing key signatures

Before to change the key signature, previous one is canceled with naturals:

Changing key signature

Finding key names from key signatures

Finding key names from key signatures with flats

With flat key signature, the last flat (♭) is always the degree IV of the major scale:

Finding key names from key signatures with flats

So with six flats, the key signature refers to G flat Major scale (or his relative minor key E flat minor):

Key signature identification with flats example 1

Finding key names from key signatures with sharps

With sharp key signature, the last sharp (♯) is always the degree VII of the major scale:

Finding key names from key signatures with sharps

So with seven sharps, the key signature refers to F sharp Major (or his relative minor key D sharp minor):

Finding key names from key signatures with sharps

Examples of key signatures in famous works

Mozart, Introitus from Requiem

The Introitus from Mozart's Requiem has only one flat on key signatures for strings instrument and a null key signature for the basset horns in F (corni di bassetto) because it is a transposing instrument.Introitus from Requiem, Mozart

This royalty-free extract was recorded in 1951 by the Wiener Philharmoniker orchestra, conducted by Josef Krips (source, CC0 1.0 Universal (CC0 1.0)
Public Domain Dedication license
).

Dvořák, From the New World, Largo

The movement Largo from the symphony n°9, also called From the New World Symphony, by Dvořák use a five flats key signature:

Dvořák, From the New World, Largo

This musical sample was recorded in 2012 by The DuPage Symphony Orchestra's (source, CC BY-SA 3.0 US licence).

Chopin, Nocturne opus 15 n°2

The Nocture opus 15 n°2 by Chopin use a six sharps key signature:

Chopin, Nocturne opus 15 n°2

(Royalty free musical sample performed by pianist Samson François in 1964, Creative Commons Zero 1.0 license, source)
You will notice that this work uses a key that is not widely used: F sharp Major. You will also notice the use of an anacrusis, double sharp (measures 5,10,12), trills (measure 7), sixteenth note quintuplets (measure 3), and sixteenth note septuplets (measure 10).


External links to learn more about :

1 - https://www.dolmetsch.com/musictheory9.htm
2 - https://musicterms.artopium.com/k/Keysignature.htm


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