Why is the aeolian mode the minor scale?

Question

I've studied music theory for many years now, and one thing has always confused me about the naming methodology for the minor scale.

A major scale is based off the Ionian mode and consist of only major and perfect scale intervals.

C   D   E   F   G   A   B   C
P1  M2  M3  P4  P5  M6  M7  P8

The minor scale is based off the Aeolian mode and consist of major, minor and perfect scale intervals.

A   B   C   D   E   F   G   A
P1  M2  m3  P4  P5  m6  m7  P8

There is a mode that consists solely of minor and perfect intervals which is known as the Phrygian mode.

E   F   G   A   B   C   D   E
P1  m2  m3  P4  P5  m6  m7  P8

It seems to me that the Phrygian mode is more minor than the Aeolian scale and should be known, at least from technical terms, as the minor scale. Is there a reason why the Aeolian mode was chosen over the Phrygian mode to be the minor scale to juxtapose the major scale?

Answer 1

The minor scale is not called the "minor scale" because it is the most minor. Names don't have to accurately reflect the definition.

Modes are sometimes classified as "minor" or "major" depending on their third (a minor third usually comes with other minor degrees like the flat 7th which is common to all minor modes of the major scale). And of all the minor modes, aolian the natural minor scale (or simply "minor scale") is by far the most commonly used in western music. So if it's the one that we use most most of the time, why not simply call it "minor"?

Now why is it the most common minor scale? It's probably because it's the least dissonant minor scale, and the most stable. Dorian, for example, isn't that dissonant, but it's not that stable ; if there is no harmony or drone to support it, the brain may interpret it as a different scale (an Aolian or Ionian scale with a different tonic), like C Maj or A Min instead of D dorian. Phrygian isn't that stable either, and it's more dissonant than aolian, try improvising a melody in E phrygian (without a drone or harmony), and you'll feel like resolving it in A aolian.

Even aolian (natural minor scale), isn't stable enough sometimes to escape the pull of the Ionian mode. This is where the melodic and harmonic minor (used over a dominant V chord - e.g G7 in Cmin or E7 in Amin...) come into play. These variations of the minor scale are there to maintain consonance when the dominant is played.

Answer 2

This has to do with common practice era harmony. A minor key should consist of a minor triad on the tonic. Phrygian, Dorian and Aeolian all fit this bill.

The next most important chord in common practice harmony is the V chord and if you are a common practice era composer, you would want a good triad for your V chord. Phrygian's V chord is diminished, so Phrygian is a bad candidate for 18th and 19th century composers.

It is harder for me to see the harmonic disqualifications of the Dorian scale. But I expect that Aeolian is preferable to Dorian when writing strict common practice era tonal harmony.

Although I am fuzzy on the specifics, I am pretty sure it is Aeolian's adaptability to tonal chord progressions that makes it the "natural" minor.

Answer 3

The “minor scale” and “major scale” have originated from the church-Latin cantus mollis and cantus durus.

These terms, in turn, originated from only the names of the notes B♭ (B molle) and B (B durum). That gave rise to the name of what came to become the most prominent hexatonic scales, namely the hexacordum molle and hexacordum durum.

• Molle, F-G-A-B♭-c-d, is a subset of the G-aeolian/natural-minor scale.
• Durum, G-A-B-c-d-e, is a subset of the G-ionian/major scale.

Using those scales in such a way is quite natural when starting from a Pythagorean system. The Phrygian scale, less so (except in retrospect – the Phrygian scale being used quite a lot in metal).

Later, these scales were extended to their modern, heptatonic forms – which are in Germanic, Slavic and Finno-Ugric languages still called varieties of “Moll” and “Dur”, e.g. we call G-major “G-Dur-Skala” and G-minor “g-Moll-Skala”.

In the Romance languages, the terms didn't linger though; instead, the durus scale was described as the more major and the mollis scale as the more minor of the two scales. English went with the Italian term, Scala minore.

Answer 4

Why is the aeolian mode the minor scale?

In short

In Western music, scales are the different ways to divide an octave in order to select interesting notes, usually seven, referred to as degrees.

In such music, thirds and fifths intervals are designed to have overlapping harmonics. Major and minor scales harness this fact, they are built from 3 juxtaposed triads to maximize consonances.

Constructing C minor scale from minor triads C, F, G generates the same intervals than the Aeolian mode of C major. However a scale is not a mode.

Other common scales are not built from triads, but by tweaking the degrees of major and minor scales, e.g. to introduce a leading tone in harmonic minor scale.

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Details

In tonal systems fifths and thirds play a major role, to the point major and minor scales are generated using triads obtained from three notes separated by fifths.

E.g. C major scale is obtained by major triads C (the tonic) and two notes at 5th intervals:

We do the same to generate a minor scale, except we use minor triads. E.g. C minor:

Intervals of the natural minor scale are also these of the Aeolian mode of C major.

It seems to me that the Phrygian mode is more minor than the Aeolian scale and should be known, at least from technical terms, as the minor scale.

The Phrygian mode (1 2 2 2 1 2 2) of C major, with its minor second, is perceived as the "most minor" mode of C major, among the ones with a perfect fifth.

However Ionian, Aeolian, Phrygian, ... modes are not scales, they are modes of C major scale. For example, they have no tonic, this notion belongs to the scale. Aeolian mode of C major is not synonymous of A minor.

• The scale is based on degrees with specific properties and a whole theory based on them, the tonal system.

• A mode, in the modern sense, is a particular use of a scale. It happens Aeolian mode of C major scale has the same intervals than a minor scale and the same note sequence than A minor.

See this answer for the differences between scale and mode.

Answer 5

Key Signatures are what people are not taking note of here. C major has no sharps or flats in its key signature. A relative minor of a major scale is one that shares the same key signature because it uses the same notes its relative major. A Minor is the relative Minor of C major as it has the same key signature of no sharps or flats. It is also the 6th degree of the major scale or a minor third below its relative Major. So any major scale you chose you can work out the relative minor by going down a minor third.
If you try the phrygian as the Minor scale it simply won't work because it would start on the 3rd of the scale, so for C major it would start on E. E minor has a key signature of F sharp. F sharp doesn't appear anywhere in the key of C. So if you played the phrygian mode of C it isn't going to be E minor as it has the notes of the C major scale not the E Minor scale. However if you move a minor third down from G. (G major has a key signature of F Sharp) you will find the relative minor is E. We can also apply the Tone/Semitone formula. Every major scale has the formula between each note of the scale ascending: Tone Tone Semitone Tone Tone Tone Semitone. Still in the Key of C (C D E F G A B C) between C and D is a Tone, between D and E is a tone, Between E and F is a Semitone etc. The Natural minor scale (which is what the Aeolian Mode of C is) Tone Semitone Tone Tone Semitone Tone Tone A B C D E F G A This cannot be applied to the Phrygian scale. The Phrygian scale starts with a Semitone so it is immediately out of the Minor formula. E F G A B C D E You are also forgetting that there are 3 main types of Minor scale. The natural minor (Aeolian Mode), the Harmonic minor and Melodic minor scale. All of which have the melodic minor as the core and altered notes are put in to create the other versions.Raised 7th in the Harmonic, and Flattened 6th and 7th in the Melodic Minor ascending but then riased again descending. You cannot do this to the Phrygian as it starts with a semitone from its first note to the second and again E minor has an F sharp. If anything the Aeolian mode is the most minor as you can make three Minor scales from it. But the main point is if you had a piece of music in E minor it wouldn't fit with the key of C because of the F sharp where as the Phyrigian of C doesn't have that F sharp so makes it the Phrygian of C and not E Minor.

Answer 6

Matthew James Briggs' answer is closest. The I, IV and V chords in the aeolian mode are all minor triads making it the most useful mode for minor keys.

Answer 7

Every major scale has its relative minor, which uses the same notes. This relative minor scale is a natural minor scale, and it starts from the sixth degree of the major scale. This relative minor scale is the Aeolian mode of the major scale. So, for example, in the key of C, playing all the same major scale notes, but beginning from A, produces the A minor scale, which is the relative minor of C. While it's true that some other modes may also be minor, they are not the relative minor. Hope this helps.