How to Identify Scale of a Song from Key Signature?

Continued from Key Signature: The Basics for Beginners

This is the second post in the Key Signature: A Beginner’s Guide series. If you haven’t read Part 1 yet, please read the first post in this series before continuing. Here’s the link to that post:

<<<< Key Signature: The Basics for Beginners

In the previous post, we discussed the fundamentals of key signatures. such as:

What is a key signature, and what is its purpose?
Why can’t we just use piano letter notes to play a song?
How to write the key signature, i.e., the order of sharps and flats, and mnemonics to remember the order

In this post, we will build on those basics and discuss an important topic: what is the relationship between key signatures and scales, and how can we identify the scale of a song from its key signature?

What is the Relationship Between the Key Signature and Scale?

The Scale of a Song

The scale is made up of seven notes, which are arranged in a specific pattern. It starts on the tonic note, and the name of the scale is named after that note.

Tonic note means the first note of the scale, which is also the most important note in that scale.

So, for example, notes for C Major scale are CDEFGABC, it starts with C note and ends with C note, so C is the tonic note of the C Major scale.

Key Signature of a Song

The key signature indicates which notes are to be played as sharps or flats in a piece of music.

As we saw in the last post (Key Signature: Basics) the key signature is always written in a specific order, using either sharps or flats, depending on the type of key signature. But sharps and flats are never mixed up in one key signature.

For the sharp key signature, the order of the sharps is:

F#, C#, G#, D#, A#, E# and B#

However, in the flat key signature, the order for the flats is:

Bb, Eb, Ab, Db, Gb, Cb and Fb.

So, how to know the scale for that song by looking at the key signature, which is at the beginning of the sheet music?

How to Identify the Scale of a Song from Its Key Signature?

Key signature: one sharp

Let’s start with an example. We previously discussed how sharps always have a certain order. Therefore, if a key signature has only one sharp, it must be F#.

We also know that the G major scale has only one sharp, which is F#.

So, if a key signature has only one sharp, F#, the song’s scale is G major, which starts on the note G and includes the notes: G A B C D E F#.

Key signature: two sharps

Next, let’s consider the example of a key signature with two sharps, and as per sharps order, those should be F# and C#.

We know that D major also has two sharps, F# and C#, and its notes are D E F# G A B C#.

Therefore, if the key signature has two sharps, F# and C#, the scale of the song is D major.

The same principle applies to other key signatures with different numbers of sharps or flats.

Key signature: blank, no sharp

If there is no key signature mentioned in the sheet music, then what?

Then the scale of the song is C major, because the C major scale, CDEFGAB, has no sharp or flat notes.

Key Signature and Corresponding Scale Table

The following table shows the relationship between key signatures and scales (what key signatures go with what scales).

In this table, the first column shows the number of sharps or flats in the key signature, and the second column shows the name of the scale.

Key Signature: Scale

No flats or sharps indicates C major.

One sharp (F#) – G major
Two sharps (F#, C#) – D major
Three sharps (F#, C#, G#) – A major
Four sharps (F#, C#, G#, D#) – E major
Five sharps (F#, C#, G#, D#, A#) – B major
Six sharps (F#, C#, G#, D#, A#, E#) – F# major
Seven sharps (F#, C#, G#, D#, A#, E#, B#) – C# major

The image given below shows how sharp key signatures are written, from one sharp to seven sharps.

One flat (Bb) – F major
Two flats (Bb, Eb) – Bb major
Three flats (Bb, Eb, Ab) – Eb major
Four flats (Bb, Eb, Ab, Db) – Ab major
Five flats (Bb, Eb, Ab, Db, Gb) – Db major
Six flats (Bb, Eb, Ab, Db, Gb, Cb) – Gb major
Seven flats (Bb, Eb, Ab, Db, Gb, Cb, Fb) – Cb major

The following image shows how flat key signatures are written, from one flat to seven flats.

Key Signature to Scale Example

The following sheet music example is for the song Faded by Alan Walker. In this sheet music, we can see that there are six sharps in the key signature area. Six sharps means – F#, C#, G#, D#, A#, and E# – because we have to follow a specific order when writing key signatures.

Therefore, according to the table given above, i.e., the relationship between key signatures and scales, six sharps means the F# major scale. So, the scale for Faded is F# major. Here is a link to the full piano score for Faded:

Faded – Alan Walker – Piano Notes