Why are there 3 minor scales

Why are there 3 Minor Scales?

This is a common question amongst music theory students. Shouldn’t we have one minor scale pattern just like we have one major scale? There are several reasons why not so in this lesson we’re going to clarify what, why and how these minor scales work.

So why are there 3 minor scales? There are 3 minor scales, or more precisely, 3 variants of the minor scale because of how harmony and melody interact in tonal music. Composers change some notes of the minor scale to achieve a specific sound for a particular style.    

That word “variants” here is important. We’re not really talking about 3 entirely different minor scales here. We have one minor scale that is altered according to our musical context.

Please note that there are other forms of minor scales too. There’s the pentatonic minor, Hungarian minor, Jazz minor, Neapolitan and so on. This lesson is about the major-minor musical system. 

Why are there 3 minor scales
Why are there 3 minor scales


Where do Major and Minor Scales Come From?

Before we actually understand why there are 3 variants of the minor scale, we need to know where the major and minor scale system comes from in the first place.

This system of major and minor scales evolved out of earlier music which instead used modes. Modes have a long and fascinating history of development going back to Ancient Greece.

What’s important to us here is that just like scales, these modes are a set of notes laid out in a unique pattern of tones and semitones. It’s really easy to see these patterns using the keyboard because we can play all 7 modes using only the white keys (so no sharps and no flats). We just have to begin on a different note every time:

The Ionian mode:

Ionian mode on C

Ionian mode on C

The Dorian mode: 

Dorian mode on D

Dorian mode on D

The Phrygian mode:

Phrygian mode on E

Phrygian mode on E

The Lydian mode:

Lydian mode on F

Lydian mode on F

The Mixolydian mode:

Mixolydian mode on G

Mixolydian mode on G

The Aeolian mode:

Aeolian mode on A

Aeolian mode on A

The Locrian mode:

Locrian mode on B

Locrian mode on B

Now if we start to add a sharp here and a flat there, the modes start losing their distinct characteristics. For example, if we added an F sharp to the Mixolydian mode, we’d get what we now recognize as the scale of G major:

The G major scale

The G major scale

Or if we changed the B natural into B flat in the Lydian mode, we now get the F major scale:

The F major scale

The F major scale

This is what happened slowly in music history until by around the 17th century the music was no longer ‘modal’ but ‘tonal’. Instead of all the different modes, the new musical system is based on just two: the Ionian (now known as the major scale) and the Aeolian (now known as the minor scale).

We discuss this in detail in this lesson about tonality but really briefly, tonal music is music that works around a tonic – a fundamental ‘home’ note where melodies and chord progressions are at rest.

While the major scale (previously known as the Ionian mode) works perfectly well in the tonal system, the natural minor scale (previously the Aeolian mode) needs some small changes. These changes ensure that the music gets a more tonal sound rather than a modal one.


What are the 3 Types of Minor Scales?

First of all, the 3 types of minor scales are:

  1. The natural minor,
  2. The harmonic minor,
  3. The melodic minor.

As we’ve just learned, the natural minor scale is the same one as the Aeolian mode. So “Natural minor” and “Aeolian” are different names for the same scale pattern. Now why do we have to alter any of this scale’s notes? Why isn’t it fine just as it is?

The reason that composers needed some alterations on that natural minor scale is because of the tonal style in the Common Practice Period (that’s the music from around the 17th century till the 20th and beyond). The essence of tonal music is to establish and maintain a tonic. Let’s say we had this musical idea:

An simple idea in the key of A minor.

A simple idea in the minor scale. 

Sounds OK. Let’s change it slightly by sharpening the G and see what happens:

The raised 7th, creating a leading tone that leads to the tonic.

The raised 7th, creating a leading tone that leads to the tonic.

Do you hear the difference? It might be subtle at first but it’s definitely there! The difference is that this second version has a leading tone. The leading tone is the note that’s one semitone below the tonic and its job is to push the music firmly unto that tonic.

Raising the 7th degree by a semitone also means that the E minor chord from the original has now become an E major chord. It is now a dominant chord, ready to take us to the tonic! This is tonal music. The other version? That’s more of a modal sound.

So a quick recap: the first version of that musical idea is using the natural minor scale on A:

A natural minor

A natural minor

The second one is using the harmonic minor scale on A. As we said, the difference is that it now has a leading tone, the 7th degree is sharpened:

A harmonic minor

A harmonic minor

The issue we now have with the harmonic minor is the distance between the 6th and 7th degrees. In A harmonic minor, that’s the distance between F and G sharp. This interval is called an augmented second and it sounds awkward in melodies of this style (especially when the music is sung). 

To fix it, we can simply raise the 6th degree so that it’s now a major second away from the 7th.

The 6th and 7th degrees of the scale are raised for a smoother melody.

The 6th and 7th degrees of the scale are sharpened for a smoother melody. 

This produces a smoother melody leading up to that tonic in bar 4. And this is why the ascending form of the melodic minor scale is necessary. 

All this becomes irrelevant in the descending form of the melodic minor scale because in this case we’re not moving towards the tonic but away from it. So in the melodic minor we get the 6th and 7th degrees sharpened on the way up, but back to their normal state on the way down:

Melodic minor scale on A: 6th and 7th are sharpened on the way up and natural on the way down.

Melodic minor scale on A: 6th and 7th are sharpened on the way up and natural on the way down.

And that’s why we get 3 minor scales. The natural minor, the harmonic minor and the melodic minor. 

  1. The natural minor scale is the equivalent of the Aeolian mode. All 7 notes remain just as they are in the key signature. 
  2. The harmonic minor scale has the 7th sharpened to create a leading tone. 
  3. The melodic minor scale has both the 6th and 7th sharpened for a smooth (and convincing) ascent to the tonic. On its way back down, it reverts back to the normal state (like the natural minor). 

Just for another example, here they are in G. First the scales and then with the triads built on them. Notice that because of the possible alterations of the 6th and 7th degrees, we also get several possibilities in creating chords. The only chord that never changes, in fact, is the tonic itself. 

G natural minor:

G natural minor scale and triads built on it
G natural minor scale and triads built on it

G harmonic minor:

G harmonic minor scale and triads built on it.
G harmonic minor scale and triads built on it.

G melodic minor (ascending only). The descending form will be just the same as the natural minor. Notice also, that raising or sharpening a flattened note makes it a natural (not a sharp). In this case, the E flat becomes an E natural:

Ascending form of G melodic minor scale and triads.
Ascending form of G melodic minor scale and triads.


Common Questions about the Minor Scale

Do the three different types of minor scales use the same key signature? Yes! Since the three forms of minor scales are simple variations of each other, they use the same key signature. Any sharps, naturals or flats that are needed are written with the notes they belong to and not with the key signature. The 3 minor scales are one and the same minor key.

How can you tell whether a piece is in a major or minor key? Apart from the key signature, look at what notes are being used and how. Read the full lesson about recognizing major vs. minor here.

What is a parallel major or minor key? Parallel keys are keys that share the same tonic note. For example the keys of C major and C minor are parallel keys because their tonic is the note C. Another example: The keys of D major and D minor are also parallel keys because their tonic is the note D. 

What is a relative major or minor key? Relative major or minor key is the key that shares the same key signature. For example G major and E minor share the key signature of 1 sharp so they are ‘relative keys’. In other words, G is the relative major of E minor and E is the relative minor of G major. 

Here’s another example: F major and D minor have the same key signature: that of one flat. So F is the relative major of D minor and D is the relative minor of F major.

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