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I'm curious about a more in-depth explanation as to why the major and minor pentatonic scales are prevalent in the western music tradition (Yes, i make a claim here that some might consider debatable. Please hear me out).

I did a brief googling and the most common explanations were: "because it's easy" or "because it sounds good", or the likes. It's not that i disagree, but i feel that there probably is more to the theory than that.

For instance, why are the fourth and seventh notes omitted in a major pentatonic scale (in reference to a major diatonic scale)? It makes me wonder since both the fourth and the fifth are perfect intervals, but only the latter is kept. Is it simply because it goes along the vein of a musical tradition revolving around the I-V relationship?

I'm assuming one could argue that the seventh is left out because of the dissonant quality in relation to the root, no?

Could anyone shed some more light on why this is? I like to hear some of your thoughts on this!

  • Pentatonic is basically a modern invention, not very prevalent at all. – Neil Meyer Aug 24 '17 at 18:20
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    Related (YouTube video of Bobby McFerrin demonstrating universal human understanding of the pentatonic scales): youtu.be/Hodp2esSV9E – Todd Wilcox Aug 24 '17 at 18:57
  • @Todd Wilcox That was so awesome. Makes you wonder whether those notes are known a priori, or learned. – Erik Aug 24 '17 at 19:14
  • @Erik the pentatonic is mathematically so simple that it's hard to see how anybody could “not know it”, any more than you could possibly “not know the number 5”: even somebody who'd never heard the word “five” could still identify that number of items. – leftaroundabout Aug 26 '17 at 21:05
  • I think the origins go back to native American Indians. Their flutes were in pentatonic, maybe they just made them even intervals. Then likely adapted to western music. – marshal craft Aug 29 '17 at 15:24
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A more "proper" term for these two pentatonic scales is anhemitonic. Major and minor scales are hemitonic, meaning they contain at least one half step (or "hemitone"). Meanwhile, these pentatonic scales are anhemitonic because they do not contain any half steps.

If you think about the C-major collection:

     C D E F G A B C

We see half steps between the third and fourth degrees (E and F) and the seventh and final degrees (B and C). So we simply remove the offenders; by removing scale-degrees 4 and 7 (F and B), we create an anhemitonic scale of C D E G A C.

As for the minor pentatonic, let's just rotate that early collection to start on A instead of C, giving us an A-minor collection:

     A B C D E F G A

We again have half steps between B and C and E and F, so we again remove B and F (although this time they're scale-degrees 2 and 6) to create the A C D E G A minor pentatonic collection.


We can get a bit more advanced here and look at the interval-class content of these two (same) collections. Without getting too specific, when we track all of the different intervals between every single pitch, we see that this particular anhemitonic collection is made up of 4 perfect fifths/fourths, 3 major seconds, 2 minor thirds, and one major third. Note that there are precisely zero half steps (as expected) or tritones. From a set-theory standpoint, the interval vector is <032140>; Hanson's chemical analysis would be p4mn2s3.

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    You may want to point out what intervals you are left with when you take out those scale degrees. The Hanson analysis of the set yields p4m2ns3 which lacks intervals which most would consider dissonant. – Dom Aug 24 '17 at 16:24
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    @Richard yep. My hand writing is terrible and I screwed up a m and n. – Dom Aug 24 '17 at 16:39
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    @Tim Your guess is as good as mine; I'm not sure why it isn't "ansemitonic." (Although, now that I type it out, it does look a little too much like "antisemitic.") – Richard Aug 24 '17 at 19:22
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    J'ew know, it's a little bit close... – Tim Aug 24 '17 at 19:53
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    IMO it's quite backwards to use set theory to derive anything about how tonal Western music has evolved – except perhaps Jazz-descended styles, but certainly not something as basic as pentatonic scales. Most Western music is not sensibly constructed starting from the 12-edo set, although that set of notes can be used to play almost all Western music (or, approximate, as I prefer to call it). – leftaroundabout Aug 25 '17 at 12:08
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The major pentatonic scale is the richest scale that can be rendered above a Ⅰ pedal bass using only consonances (in a sense of “consonance” which I'll elaborate). For example on C,

  • C: fundamental/octave, obviously stable.
  • D: pure Pythagorean (9:4) ninth, not a consonance in the usual sense but actually a perfectly smooth interval as long as the bass and melody are far enough apart.
  • E: major tenth, extremely consonant if rendered in just intonation (5:2).
  • G: fifth/tritave 3:1, easily pure.
  • A: major thirteenth/sixth. This one actually works particularly good in the same octave as the bass note, namely as the 5:3 major sixth.
  • c: yet another octave, duh.

So: you have all frequency ratios with numerator smaller than 10 and denominator <5. In fact, if you list all otonal fractions fulfilling that condition, you only get a few notes that don't belong to the major pentatonic:

  • 11 — C — fundamental
  • 54 — E — third
  • 43 — F — fourth
  • 32 — G — fifth
  • 53 — A — sixth
  • 74 — B♭ — septimal seventh
  • 21 — c — octave
  • 94 — d — ninth
  • 73 — e♭ — subminor tenth
  • 52 — e — tenth
  • 83 — f — eleventh
  • 31 — g — twelfth
  • 72 — b♭ — septimal fourteenth
  • 41 — c' — 2 octaves
  • 92 — d' — 8ve+9th
  • 51 — e' — 8ve+10th
  • 61 — g' — 8ve2+5th
  • 71 — b♭' 8ve2+₇7th
  • 81 — c'' — 3 octaves
  • 91 — d'' — 8ve2+9th

In particular, the range from G to e (which is quite a typical domain for a pentatonic melody) is exactly the pentatonic scale if you leave out those foreign 7-limit intervals. The F would of course be a rather natural candidate too, but observe that in my system it only occurs in the low octaves, so it's a more natural choice for the bass to jump to (which indeed it often does in folk tunes) rather than the melody.

The septimal seventh is somewhat disqualified in Western music because it can't be approximated by many instruments. This is quite different in many styles around the world.

You may ask what's special about “numerator <10 and denominator <5”. Well, those exact numbers are certainly a bit arbitrary, but actually you will find that the ninth overtone is about the highest that can be reliably played as a flageolett on string instruments. (I believe most brass instruments can also play the 9th overtone fairly well but get into trouble if trying to go much higher, but not sure, I don't play any brass.) Also, three octaves are quite a typical range “in which most music happens”, traditionally – anything lower or higher is more of a sonic-effect thing.

That's not to say that anything which can't be written as a <10 fraction is necessarily immediately much more consonant. In particular, the 15:8 major seventh is actually a good contender to the 9:8 ninth – in particular, the major seventh chord sounds very sweet. But that relies on the proxy-quality of the chord construction: the major seventh can readily be constructed as a third over the fifth in a normal major chord. This kind of construction doesn't really work for a more intuitive, improvisational, single-voice-over-pedal approach.

As for intervals like the 7-limit sevenths, and also slightly higher limits like 11 or 13: those are found in some music, in particular Indian, Persian and Arabic music. The problem with these is that if you actually devise tuning systems that allow rendering them on fixed-frequency instruments, you pretty much have to commit to one single key, else it gets very complicated. Western music evolved to also embrace modulations. Those can be nicely incorporated if you only consider the 5-limit intervals, which is probably the reason why we have never found much use of the 7-limit intervals. Except we have, actually: the harmonic seventh is all over Barbershop singing, and the subminor third and 7:5 or 11:8 tritones are arguably the prototypical blue note intervals. Just, you don't get to write down such intervals exactly in the Western system, so they remain considered as more of an embellishment.

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    It should perhaps be mentioned that while this pentatonic scale consists of intervals which are all consonant with the tonic C (if you consider 9:8 consonant with 8:8, which is not unreasonable), the interval between the D (9:8) and A (5:3) is the classic wolf fifth, 40:27. – Scott Wallace Aug 26 '17 at 18:52
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    @ScottWallace indeed. Which adds to the verdict that the pentatonic is mostly a “monophonic scale”, great for freely developing a single voice over a static accompaniment but not all that useful for writing counterpoint. – leftaroundabout Aug 26 '17 at 20:59
  • yep. Of course, you can tune your pentatonic scale to equal (or meantone, etc) temperament and smear that wolf over a wide area, but then you are left with no advantage over heptatonicity as far as sound goes, and impoverished in the number of scale steps you have for making effective counterpoint. – Scott Wallace Aug 27 '17 at 9:12
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You are operating under a standard-harmony bias. The pentatonic scale is not a major scale with notes missing it is simply a scale with 5 notes, Penta means 5. It is useful for modern music because its wide intervals make for greater harmonic leeway, but on the other hand, its bare-bones harmony makes it in one sense naked. This is why it often has notes added to it.

It is relevant to the modern genres because, with each new passing of the musical era in the west, there comes a need for the theorist to reinvent the wheel. Now with the pentatonic scales limits in mind, we should still respect it for the big paradigm shift it enabled.

Although I mainly operate under the guise of standard harmony I must say the paradigm shift in music in the 20th century, that was enabled by this scale was a rather brilliant. Jazz, Rock, Blues... all these things take from this piece of harmony. We should all be glad it exists.

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    There is nothing "modern" about the pentatonic scale. Western Baroque and Classical music are the exception, rather than the norm, in their avoidance of pentatonic harmonies. – Kyle Strand Aug 24 '17 at 20:13
  • I like neils answer, @Neil Meyer wasn't native Americans who developed it. Probably just put four evenly spaced wholes for da fingers, so gives 5 notes if you refer the workings of a flute. Then westerners came along, and probably used it for inspiration, to give a new feel that described contemporary America and what better than the music of the Indians they took it from. – marshal craft Aug 29 '17 at 15:30
  • @marshalcraft what better than the music of the Indians they took it from - Source? Are you saying the African slaves adopated their work songs and chants from the native americans?! AFAIK, It's quite well documented that the pentatonic was absorbed into modern culture through African Americans. IMO the evidence indicates the opposite: traditional American music from whites, although they had more contact with the N-A's than blacks, tends to avoid/minimize pentatonic scales and harmony. Traditional country music, bluegrass etc use decidedly Major/European oriented structures and harmonies. – Stinkfoot Sep 1 '17 at 0:59
  • @marshalcraft Pentatonic scales existed in the majority of musical cultures, not just in the Americas: en.m.wikipedia.org/wiki/Pentatonic_scale#Pervasiveness Even in Western classical music, pentatonic scales aren't particularly related to "contemporary America". – Kyle Strand Sep 4 '17 at 9:20
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If you start at C and go up in 5ths and stop after 5 notes (before the M7 interval), that is all of the notes of the pentatonic scale out of order. C>G>D>A>E 5ths are the most pleasing interval (other than the octave) so you just have one pleasing interval and then it's most pleasing interval and so on til you get 5 notes. Then you can reduce the above notes down by octaves so all notes are within the roots octave range so you get a scale C D E G A (C). That's why it sounds so freakin good, because there isn't an unpleasing note in the bunch.

  • You've lost the tritone, that's all. This explanation has been aired many times, and is just co-incidental. – Tim Aug 29 '17 at 5:58
  • "You've lost the tritone, that's all." What about the other 6 lost ones? – Rolf Aug 29 '17 at 13:51
  • You quoted C,D,E,G,A. You must have lost the others somewhere!! They were never in the equation you came up with. – Tim Aug 29 '17 at 15:17
  • Yes thank you sir! I will clarify. I intentionally lost the tritone (F#) , including all the other notes but more specifically the 4th (F) and the 7th (B) that was asked about because I stopped after 5 notes since it is a pentatonic scale. They are in the equation, which is the glorious circle of 5ths. C > G > D > A > E > B > F# > C# > G#/Ab > Eb > Bb > F > (C). The beauty is that is is the first 5. – Rolf Aug 29 '17 at 16:01
  • The phenomenon happens on any consecutive five. Take D A E B F#. In 'alphabetic' order, D F# E A B - D maj. pent. So it's not that remarkable. A triton needs two notes, and you didn't lose F#, you lost the F-B/ B-F, which is the tritone out of C maj., thus ending up with C pent. maj. pent. – Tim Aug 29 '17 at 16:46
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I am no expert but I'm surprised no one has mentioned this....

Most articles I have read explain that pentatonic scales are elementary starting scales for students to quickly adapt to any instrument.

Once the student has acquired skillful pentatonic scales, they can complete their training with incorporating the seven note scales.

I believe this method for education purposes would keep their student attentive and practicing, without initially feeling lost.

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The reason for the prevalence of the pentatonic scale in modern Western music is that Western pop and folk music of the last century has centered around the guitar and pentatonic scales are extremely easy to play on the guitar.

Both major and minor pentatonic scale patterns on the guitar have the same shapes but are centered on different frets and start on different on different notes. For example the minor pentatonic A scale starts on fret 5 and the lowest note is A. The same shape will give you the major pentatonic A scale on fret 9 with the lowest note C#.

The notes (scale degrees) for each chord in a standard I-IV-V chord progression are:

  • I : 1 3 5
  • IV: 1 4 6
  • V: 2 5 b7

Minor pentatonic scale: 1 b3 4 5 b7

Major pentatonic scale: 1 2 3 5 6

Assume the avoid (really dissonant) notes are all minor 2nd intervals; that is, all the notes to avoid playing at the same time are a semitone or one fret apart.

Then the minor pentatonic avoid notes for each major chord are:

  • I: b3
  • IV: 6
  • V: 2

So on a pentatonic scale you only have worry about avoiding one note per chord.

A common trope on the guitar is to switch between major and minor chords, swapping a I for a Im (i) chord, for example. Likewise a common trope is to switch between minor and major pentatonic scales when soloing.

Years of listening to the pentatonic scale and these tropes has taught the listening audience to easily accept major 2nds as harmonically acceptable and to accept minor 2nds as acceptable passing tones. If a guitar player accidentally hits a minor 2nd they can easily correct by sliding or bending the note to a major 2nd.

A guitar player with limited skill can quickly be playing some rather tasty melodies and solos over a I-IV-V chord progression using pentatonic scales. Roger Waters--who is quite skilled--has made a career of playing distinctive pentatonic solos.

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    Use of the pentatonic in blues pre-dates the popularity of the guitar. Some trace the use of the pentatonic in American slave field hollars/songs from the Muslim call to prayer. – Todd Wilcox Aug 24 '17 at 19:07
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    I'm expressing skepticism that the reason why pentatonic scales are prevalent is because of the popularity of the guitar. There are reasons to believe the popularity of each is not related to the other at all. If the guitar had never existed, the cultural heritage of the most popular music of the 20th century would still have been heavily influenced by black American slaves and sharecroppers. African-American culture pervades American culture and American cultural imperialism is one of the major aspects of the 20th century. – Todd Wilcox Aug 25 '17 at 1:18
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    See also: the black keys on the piano. – Richard Aug 25 '17 at 5:54
  • Yep. Pentatonic scales are worldwide and ancient, going back at least two millennia and probably much further. It seems very unlikely that their popularity in modern Western music has anything to do with the guitar. – Scott Wallace Aug 26 '17 at 19:02
  • If we agree to your debatable contention that pentatonic scales are easier on guitar, the opposite might be true: The guitar has become extremely popular because it's a good instrument to use for playing pentatonic scales and modern genres of the 20th century, engendered by, and closely linked, to pentatonic scales. As the other comments have said, pentatonic scales were in widespread use long before the guitar was. (The invention of the electric guitar, perhaps the most versatile, flexible and easiest to play instrument in history was also a huge factor in the modern rise of the guitar.) – Stinkfoot Aug 30 '17 at 10:34

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