Music Theory: Why are there 3 minor scales?

My students sometimes ask me, “Why are there three different types of minor scales, when there’s only one type of major scale?”

Another question I often hear is, “Why does the melodic minor scale have different notes going up and going down?”.

In this post I’ll attempt to answer to both of those questions.

If you’re like me, the first scale you were taught when you began learning an instrument was a major scale. Depending on the instrument, it might have been the C major, G major or F major scale. Then, a little later, you were taught minor scales. The first minor scale I learnt was a harmonic minor. Later I learnt the melodic minor, and later still, the natural minor. I don’t really know why I was taught the scales in this order – thinking about it now, it seems more logical to start with the natural minor – but I know that, like me, a lot of people learned the scales in this order.

To understand how we came to do things this way, we need to know a little bit of history.

These days we tend to think of songs as being in either a major key or a minor key. While we understand that there are many different types of scales and chords, we generally identify tonality in the context of what I call the major/minor duality. We also know that we can transpose any scale, chord or song into any one of 12 different keys.

But musicians didn’t always think this way. Our modern concepts of transposition and the major/minor duality only go back around 400 years. That seems like a long time to us, but in the grand scheme of things, it’s fairly recent.

A page of medieval sheet music. Notice the square note-heads; and how some of the staves have five lines, while others have only four. Five line staves didn’t become standard until later.

Medieval Modes

During the Medieval period, our modern idea of transposition didn’t exist. Instead, the quality of a piece of music was tied to its tonality. In other words, the type of scale you used was dependant on the “key” you were in. (That’s putting it in modern jargon, because our modern idea of keys didn’t exist yet either.)

Imagine you have a keyboard without any black notes. You have all the keys from C to C, but none of the sharps or flats. You could play a C major scale, but if you tried playing a scale from D to D the intervals between the notes (ie. the tones and semitones) would be arranged in a different order, so the scale would have a different quality – Dorian. Similarly, if you played from E to E you would get a Phrygian scale, and so on.

This is not too different to our modern understanding of modes, except for one thing: with our modern chromatic keyboard we can play a Dorian scale starting on any note. We can play F Dorian, or G Dorian, and so on. But with only the white notes, the only way to get a Dorian sound is to start on D. Start on a different note, and you’ll get a different type of scale. If you want the melody to have a Dorian quality, it has to have D as its tonal centre. That’s what I meant when I said “the quality is tied to the tonality”.

In truth, since these concepts were developed around acapella vocal music in the early medieval church, the pitch wasn’t necessarily fixed anyway. From one day to the next, they might have sung the same melody slightly higher or lower in pitch. They were concerned with the quality of the scales and intervals, not with absolute fixed pitch.

Over time, musical instruments became more important as accompaniment to singing. As a result, pitch became more fixed (although still not as fixed as today) which eventually lead to our modern concept of keys. Also, musicians progressively added more semitone intervals to their scale, leading to the chromatic scale that we know today, and giving rise to the concepts of transposition and modulation. With these developments, the old medieval modes fell out of favour, and they didn’t really come back until jazz musicians re-discovered them in the mid-20th century. Needless to say, jazz musicians use these modes in a very different way and in a very different context than how they were originally employed 1000 years ago.

The Rise of Chords

While most of the old modes fell out of use, two of them became the backbone of our modern major/minor duality: Ionian (which we now call the major scale), and Aeolian (which is our natural minor scale). This coincided with the reorganization of harmony to a vertical, rather than horizontal, model.

You see, musicians in the late Medieval and Renaissance periods had an appreciation of harmony, but they didn’t think in terms of chords the way we do today. They knew that when certain notes were played together they sound good, whereas other intervals sound discordant. They devised a system of counterpoint (commonly called “species counterpoint”) that allowed them to create independent melodies that sound good together. This type of polyphony is a very linear, horizontal way of looking at harmony.

By contrast, our modern approach to harmony is more vertical. We stack notes on top of each other to create chords, which we label with names like A major 7, F# half-diminished, and so on. We think in terms of chord progressions, playing these predetermined chords one after another. This vertical chordal approach is very different to the concept of harmony embedded in the “species counterpoint” which was common during the Renaissance. Our modern idea of arranging the notes vertically dates back to the Baroque era when composers began writing basso continuo, or “figured bass” which is, in essence, the earliest type of chord chart.

The Perfect Cadence

The development of chord structures naturally lead to the idea of cadences. A cadence is when one chord resolves to another. There are different types of cadence, depending on which chords we use. The most common type of cadence is when we play a dominant chord (ie. the chord built on the dominant note) followed by the tonic chord. This is called the “perfect authentic cadence”. Some people refer to this simply as the “authentic cadence” or the “perfect cadence”. I prefer the latter. The vast majority of cadences are perfect cadences.

The perfect cadence is a very important sound in western music. It’s the most effective way to create a sense of tonality. When we hear the tonic chord it feels like home. The reason the tonic chord has such a strong sense of “arrival” is because of the way the dominant chord has prepared the way for it. The dominant chord creates a harmonic tension, and the tonic chord is the resolution of that tension.

The perfect cadence below is in the key of D. It has a dominant chord (the A7 chord – A, C#, E, G) leading to the tonic chord (the D major chord – D, F#, A).

(Note: the perfect authentic cadence normally includes a bass-line with the root notes of the chords – A to D. I’ve omitted the bass clef part to save space.)

You’ll notice that the E in the dominant chord resolves down to the D in the tonic chord. The G also resolves down, landing on the F# in the tonic. But the C# resolves up, moving to the D in the tonic chord. Having the C# resolve upwards while the E and G resolve downwards creates a contrary motion that is pleasing to our ears because it implies independence between the moving lines. But there’s another reason the C# resolving upwards is important.

If you play an ascending D major scale, the C# is the 7th, and second last, note. It’s a semitone away from D, which is the tonic. That fact is important because there is a real sense of the C# pulling upwards to the D. Try this: Play an ascending major scale, but stop on the seventh note. For example, play: D, E, F#, G, A, B and C#. You’ll feel an almost irresistible urge to finish the scale by playing the high D. You just can’t leave that C# hanging there – it demands resolution! For this reason, the seventh note of the scale is called the “leading note” – because it leads us up to the tonic.

Now try this: Play the same scale again, but this time substitute C natural in place of C#. Play these notes: D, E, F#, G, A, B and C. You’ll find that the C doesn’t have nearly as strong a sense of pulling upwards to the D. It doesn’t feel like it needs to resolve up. You can just sit on that C all day and it doesn’t feel any particularly strong pull in either direction – not like the C# did. The scale with the C natural is called Mixolydian. It’s one of those modes which fell out of use at the end of the medieval period, and the reason it fell out of favour is because of its lack of harmonic direction, as you’ve just observed.

Cadences in Minor Keys

As we’ve just seen, a large part of the reason perfect cadences are so effective is because of that semitone interval between the leading note and the tonic. The way the leading note wants to pull up to the tonic makes the dominant chord want to resolve to the tonic chord, because the leading note is in the dominant chord.

That’s fine in major keys, because the leading note in a major scale is a semitone away from the tonic. But when we look at minor keys, we notice a problem. As I said earlier, our natural minor scale is actually the old Aeolian mode. Here it is in the key of D minor:

The problem is that the leading note is a whole tone away from the tonic. In D minor, the leading note is a C, whereas the tonic is a D. Remember earlier when you played the Mixolydian scale and you realised that the leading note didn’t have same strong pull upwards to the tonic because it was a whole tone away? Well, it’s the same thing here. We can make a perfect cadence using the notes of the natural minor scale, but without that semitone leading note, the dominant chord just doesn’t have a strong desire to resolve to the tonic. Try it for yourself:

(Note: as with the previous example, the bass clef part has been omitted to save space.)

See how the Amin7 chord is perfectly happy to sit there unmoving? It doesn’t feel like it has to resolve to the tonic chord, as it did in the major key. We would say that this cadence has a fairly weak resolution.

This was a problem for composers in the early Baroque period. They really wanted a much stronger cadence for their pieces in minor keys. Fortunately, the solution was pretty simple – they just used the dominant chord that had worked so well in the major key. By borrowing the A7 chord from the key of D major they had a much stronger perfect cadence: V7 to I minor.

This perfect cadence works better because we’ve now got that all-important semitone from the leading note (C#) to the tonic (D). Since the key signature of D minor doesn’t have a C# in it, we need to add in the sharp as an accidental. (An accidental is a sharp, flat or natural which is not in the key signature.)

The Harmonic Minor Scale

If we arrange all the notes from those two chords into a scale we get the D harmonic minor scale. We’ll also add the Bb, as indicated by the key signature:

The important thing to remember about the harmonic minor scale is that it was developed so that the chords will make a better cadence. In other words, the harmonic minor was invented for making harmonies. That’s where its name comes from. If you build a triad starting on each note of the harmonic minor scale you get the following chords:

As you can see, there are two minor triads, two major triads, two diminished triads, and one augmented triad. For centuries composers have constructed great sounding chord progressions in minor keys using these chords, commonly extending the V triad to four notes to make a V7 chord. In particular, the use of the I minor and IV minor chords (in this key: D minor and G minor) creates a real sense of the minor tonality, whereas the V or V7 chords (A major or A7) gives the strong perfect cadence resolution.

The Problem with the Harmonic Minor Scale

There is a problem with the harmonic minor scale, though, and it’s a problem which might be difficult for us to understand today. In order to really comprehend the problem, we have to understand a few things about society in the 17th and 18th centuries.

You see, Baroque composers couldn’t write melodies with the harmonic minor scale. That’s to say, you can write melodies with it – of course you can – but European musicians back in the early baroque era had a problem with those types of melodies. The problem is with the interval between the 6th and 7th notes.

You see how the 6th note is a B flat, whereas the 7th note is a C#? That interval is called an augmented 2nd. It’s a 2nd, because B is right next to C in the alphabet, but it’s an augmented 2nd because the interval between those notes is three semitones. The scales we use most commonly are generally made up of whole tone and semitone intervals. That means – each note is usually one or two semitones away from the next note. Scales with augmented 2nd intervals (ie. three semitones) are pretty uncommon. (Pentatonic scales have intervals of three semitones, but that’s because there’s a note missing, so its actually a minor 3rd, not an augmented 2nd.)

When you play a harmonic minor scale, those top few notes have a very particular sound. It sounds kind of exotic, like something from the Middle East. I really like it. In my mind it brings up an association with Arabic or Egyptian music, and there’s a reason for that. This sound, the augmented 2nd with a semitone on either side of it, it a common feature of melodies in Arabic, Hebrew and Egytian music. In Arabic and Egyptian music it occurs in a scale called Hijaz Maqam or Hijaz Nahawand. In Hebrew music is occurs in a scale called Ahava Rabbah, also called Freygish in Klezmer music. It even occurs in Indian Ragas.

These associations with Arabic music are why the augmented 2nd interval sounds kind of exotic to me. That’s why I love it, but its also why European composers in the Baroque era avoided it. To understand why, you need to know a little bit more about the history of Europe and the Ottoman Empire.

Suleiman the Magnificent, Sultan of the Ottoman Empire.

The Ottoman Empire

During the late medieval period and into the Baroque era, the Western European nations were waging a long running war against the Ottoman Empire. Under the reign of a Sultan called Suleiman the Magnificent (1494-1566), the Ottoman Empire became incredibly powerful and prosperous. Suleiman controlled most of the Middle East and northern Africa as far west as Algeria. His fleet dominated the seas from the Mediterranean to the Red Sea and through the Persian Gulf. He made moves on Europe as well, conquering most of Hungary, annexing Belgrade in modern day Serbia, and Rhodes in Greece, and laying siege to Vienna in 1529.

Not only was the Ottoman Empire a threat to Europe because of their military might, there were strong cultural and religious differences between the Europeans and the Ottomans. You see, the Ottoman Empire was an Islamic empire, whereas the European nations were Christian. Europeans saw the struggle against the Ottomans as being about more than just political power and military might. They saw it as nothing less than a holy war. The Europeans knew that wherever the Ottomans conquered, the populace would be converted to Islam. For the Christians of Europe this was nothing less than a struggle for the salvation of their eternal souls. Pretty heavy stuff!

The Melodic Minor Scale

In the midst of all this, musicians were developing the harmonic minor scale as a way to develop chord progressions in minor keys, but with all the cultural baggage of that very Arabic sounding augmented 2nd interval, they were reluctant to use it for making melodies. It was important to them to define their European culture as being different to Islamic culture, and this played out in music as it did in every other aspect of life. They considered themselves to be more civilized to Muslims, who they considered “barbarians”.

(Side note: The word barbarian means “person with a beard”. It’s where we get the English word “barber” (one who shaves beards) and the French word “barbe” meaning “beard”. The fashion in Europe at the time was for men to be clean shaven, whereas Muslim men traditionally wear a beard, which is why the word barbarian came to mean “uncivilized”. In the 1982 film Conan the Barbarian, Conan – played by Arnold Schwarzenegger – is clean shaven. So really, he wasn’t a barbarian at all. The film makers got that wrong.)

This left musicians with a dilemma: how do you include the raised leading note which was so important for the harmonic movement of European music, without making your melodies sound like an Arabic maqam?

The solution was to raise both the 6th and 7th scale degrees, thereby eliminating the augmented second interval, while still maintaining the all-important raised 7th. This requires adding two accidentals to the scale. In the key of D minor, the B flat in the key signature must be raised to a B natural, and we raise the C to C#, as with the harmonic minor scale. We call this the melodic minor scale because it’s better for making melodies.

So, problem solved. We have a minor scale with a raised leading note and no augmented 2nd intervals. We’ve even got a snazzy new name for it. We’re all good now, right?

Well, not exactly.

You see, the problem with the melodic minor scale it that it just doesn’t sound all that… well… minor. Sure, it has a minor 3rd degree, so the bottom part of the scale has a nice dark, minor quality. But by raising both the 6th and 7th notes, we’ve made the top part of the scale indistinguishable from a major scale. In fact, the ascending melodic minor scale has only one note that is different from it’s parallel major scale – the 3rd. As a result, melodies constructed with this scale don’t have that lovely rich dark sound we associate with minor tonalities. They sound just a little too…. bright!

What to do?

The solution was to revert back to the natural minor scale when the melody is descending. You see, the whole point of inventing both the harmonic minor and melodic minor scales was to get that raised 7th happening. And the reason the raised 7th was so important was because it has that strong sense of pulling up to the tonic above. But when the melodic phrase is going down that isn’t really an issue. We’re not striving upwards to reach the tonic anymore. Rather, we’re moving away from the tonic by heading downwards, so we don’t have the same imperative to raise the leading note. By reverting back to the natural minor – the mother of minor scales, if you will – we lower both the 7th and 6th notes to where they were before we started messing with them in the first place. This gives us more of a minor quality to our melodies in descending phrases. This is why the melodic minor scale is the only scale in western music which has different notes going up, to coming down. Cool, huh?

(Another side note: Just as jazz musicians in the 20th century rediscovered the old medieval modes, they also rediscovered the ascending form of the melodic minor scale. When the ascending form is played both up and down, it’s sometimes called the “Jazz minor scale”. As you can probably guess, this is fairly recent terminology.)

Conclusion

Well, we’ve come to the end of this rather long winded explanation of why there are three different kinds of minor scale, and we’ve also explained why the melodic minor scale has different notes going up to when it’s coming down. There was a bit of history involved, but that’s not a bad thing. I always think its interesting to discover how things came to be the way they are.

The important things to remember are:

The harmonic minor scale was invented for creating harmonies.

The melodic minor scale was invented for creating melodies.

The natural minor scale gets its name from the fact that it doesn’t have any accidentals.

If you’ve got any music theory questions you’d like me to answer, leave a comment or drop me an email. I’ll do my best to answer them for you.


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