Key Signatures & Scales

This is such a key (haha) theory item I thought it deserved its own page.

What is a Scale?

Fundamentally, a scale is a set of notes played in order that all belong to one key. Each scale also has a tonality. Here I will focus on Major and Minor tonalities (but do investiage Modes for very exciting, different sounding scales).

The Major Scale

Each Major Scale, whichever note we start on, always has the same intervals/steps between each note. This is what makes it sound major!

The gaps are the following:

  • Tone
  • Tone
  • Semi-tone
  • Tone
  • Tone
  • Tone
  • Semi-tone

A scale always has each note from the musical alphabet but has to follow these gaps to be sound right, and so whatever note we start on we need to use accidentals - sharps or flats.

The Minor Scale(s)

Minor scales also have set intervals, but they are a but more sneaky.

The Natural Minor

For a Natural Minor Scale the gaps are as follows:

  • Tone
  • Semi-tone
  • Tone
  • Tone
  • Semi-tone
  • Tone
  • Tone

In this way A minor has the following notes:

  • A B C D E F G a

E minor

  • E F# G A B C D e

Bb minor

  • Bb C Db Eb F G Ab bb

The Harmonic Minor

Although this is the natural minor, most of the time we hear a minor scale or minor key the 7th note of the scale is sharpened. This is not included in the key signature but instead as an accidental. When this is done, this is called the harmonic minor.

If in a flat key signature a flat needs to be raised, this is shown as a natural sign.

The Melodic Minor

But those naughty Musicians didn't stop there. Not content with how unperky the harmonic minor sounds the melodic minor was born.

This sneaky scale has is different ascending to descending (damn them!).

Ascending: sharp 6th AND sharp 7th


Practically, this means when writing out a melodic minor you have to be really careful of your accidentals

What is a key signature?

Imagine you are someone who writes out scores back in the 17th century. There are no computers to do this for you. Everything is by hand. You just want your music to stay in D major all the time. So are you going to have to write out a # EVERY time you see an F or C...HOW ANNOYING.

Fear not! For the Key signature is here! Hurrah!

Score writers, or Engravers (ooh fancy!) worked out you could write the #s or bs at the start of the stave that were part of the key instead of writing them out every time. And thus the key signature was born.

The key signature indicates which #s or bs belong to that key and should therefore be used consistently.

I am looking at a key signature. What key is it?

There are two parts to this question - what the key signature is telling us and whether it is major or minor.

You have two options to answer for a Major key.

Option 1:

  • Learn all your key signatures off by heart.

You could use this circle of fifths (more on this another time) to help. The more you look at key signatures them the more you will recognise which they are

Option 2:

  • Know how to work it out

Sharp Keys

  • Look at the final sharp. This is actually the 7th note of the scale
  • Add 1 semi-tone to this note and you get the key name
  • E.g. Final sharp = F# Key=G major
  • E.g. Final sharp = D# Key= E major


If the key has no sharps or flats it is C Major

If the key has one Fffffffffflat, it is F Major

Flat Keys

  • Look at the penultime (one before last) flat
  • Whatever this is, that is the name of the key.
  • E.g. Penultimate flat = Bb Key=Bb major
  • E.g. Penultimate flat = Db Key= Db major

Hold on two ticks... It could be Minor! How would I know?! And what would the key be?!

Minor Keys can be more tricky.....

To work out that a piece of music might be a Minor Key there are three routes:

  • Listen to it - a minor key will clearly sound less perky
  • What is the first and last note of the bass line? This will (likely) be the tonic. If it is not the same as the name of your (major) key it is likely to be minor
  • Do you see extra #s written in the score? This might indicate a sharpened 7th.

If you see any of these you can work out the Relative Minor. This is the minor key which shares the same key signature as a major key.

How do I work out a Relative Key?

Each key signature has two keys associated with it - one major and one minor.

Each key has chords associated with it and we number these I II III IV V VI and VII to match the 7 different notes of the scale. When we use a capital number this is a major chord. When we use a little number this is a minor chord.

In a Major Scale the chords follow this pattern:

  • I ii iii IV V vi vii(dim)

In a Major key Chord vi is the Relative Minor

  • So to work out the Relative Minor, count up to the sixth note in the scale.
  • E.g. In C major the 6th note is A, so A Minor is the relative minor
  • E.g. In G major the 6th note is E, so E Minor is the relative minor
  • E.g. in Eb major the 6th note is C, so C Minor is the relative minor

In a Minor Scale the chords follow this pattern:

  • i ii(dim) III iv v VI VII

The same relationship has been held between the chords, but now all the chords have been moved along. Therefore:

In a Minor Key Chord III is the Relative Major

  • So to work out a Relative Major, count up to the third note in the scale
  • E.g. In A Minor the 3rd note is C, so C major is the relative major
  • E.g. In E Minor the 3rd note is G, so G Major is the relative major
  • E.g. In C Minor the 3rd note is Eb, so Eb Major is the relative major

What is that 'dim' all about?

A diminished chord - a scary sounding chord where all the intervals are minor 3rds. Make a minor chord, but then bring the last note down one semi-tone.

I have to draw the key signature. What accidentals do I need?

Work out what #s and bs the key signature needs by using by working out what key it is (see above). You can work this out from the first note (be careful of minor keys!)

If a question asks you to draw the key signature, make sure the #s or bb are written in the correct order:

Sharp key signatures #








Flat key signatures b








If you are asked specifically NOT to write the key signature out (on a scale for example) you will need to write the accidentals next to the correct note.

How can I improve my knowledge of key signatures?

Play this game! You can change the settings and difficulty on the cog.