Pentatonic Scales and the Blues

Every scale so far has had seven notes. This lesson is about scales made by taking notes away.

A five-note scale is a pentatonic. It looks like a simplification, and in one sense it is — but which two notes get removed is not arbitrary at all.

Remove the notes that made the half steps

The major scale had exactly two half steps, between degrees 3–4 and degrees 7–8.

Take out the fourth and seventh degrees and both half steps vanish with them.

The remaining gaps run whole – whole – minor 3rd – whole – minor 3rd. The smallest step is a whole step, which means there is not a single half step in the scale.

That is the essential property. As the previous unit established, the minor 2nd is the most severe dissonance available, and here it cannot occur by construction. No two notes of the scale, sounded together, can clash badly.

What the absence of half steps buys you

▶Pentatonic pair (C–E)▶Pentatonic pair (D–G)▶Pentatonic pair (E–A)▶Major-scale half step (E–F)

Check: The first three are arbitrary pairs drawn from the pentatonic scale; the fourth is the E–F half step that exists in the full major scale. The pentatonic pairs are all acceptable no matter which you pick, while the last one grates immediately. That is the whole reason pentatonic playing is so hard to get wrong.

major 3rd — consonant

It arose independently around the world

Pentatonic scales turn up in cultures with no historical contact: Chinese traditional music, Japanese folk song, Scottish and Irish melody, African-American music, the Andes, Indonesia.

The leading explanation for that convergence is the property just demonstrated — no half steps.

• notes rarely clash when sounded together → ensemble playing and improvisation are easy
• adjacent notes are widely spaced → melodies are singable and memorable
• fewer notes → instruments are simpler to build and tune

So a pentatonic scale is not a degraded seven-note scale. It is a structure optimized for ease of use. That optimization has not expired either: the large majority of rock and pop guitar solos are built on pentatonics, and they remain a front-line tool.

The minor pentatonic is the relative form

The relative relationship carries over intact.

Take the notes of C major pentatonic (C D E G A) and reorder them starting from A to get A C D E G. That is A minor pentatonic.

Measured from the tonic it runs 1 – ♭3 – 4 – 5 – ♭7. The minor 3rd and minor 7th give it its minor-side character.

That the two share a pitch collection matters enormously in practice. A guitarist who learns one shape for “the A minor pentatonic position” has simultaneously learned “C major pentatonic.” One fingering, two keys.

Check

Which minor pentatonic uses the same set of notes as G major pentatonic?

BDEF#

Check answer

The blues scale — a note from outside the theory

Add one note to the minor pentatonic and you get the blues scale. The addition sits between the fourth and fifth degrees, a ♭5 above the tonic.

On C that gives the six notes C E♭ F G♭ G B♭.

That ♭5 is the blue note, and the important thing about it is that functional harmony cannot account for it.

• it is not in any major scale
• it is not in natural, harmonic, or melodic minor
• no harmonic explanation such as borrowing applies

And it is nonetheless indispensable in blues and rock. The reason is that the pitch sense of the blues never fit inside twelve-tone equal temperament to begin with. In blues singing, and in guitar bending, the ♭3 and ♭5 are produced at pitches noticeably off the tempered grid. The blues scale is a keyboard approximation of notes that equal temperament cannot hold.

Which is why the blue note is treated as a note in transit rather than a place to stop. You slide F → G♭ → G, or bend from G♭ up toward G. Keeping it moving is how the departure from the tempered grid gets expressed.

The blue note is a passing note

▶Minor pentatonic▶Passing through ♭5▶Stopping on ♭5

Check: First the plain minor pentatonic going up. Then the same line with ♭5 inserted so it passes F → G♭ → G. Then a version that stops on the ♭5, which sounds unresolved and stranded. The contrast makes it clear this is a note that has to move.

five notes

Check

Why is the blue note (♭5) difficult to explain within functional harmony?

Because you cannot build chords on itBecause it cannot be notatedBecause it is too lowBecause it belongs to neither major nor minor

Check answer

Subtraction and addition as general operations

Stepping back, this lesson has demonstrated that scales get built in two directions.

• subtract: seven notes → five (remove half steps, make the scale forgiving)
• add: five notes → six (introduce a note from outside to widen expression)

That frame carries straight into the next lesson on Japanese and Asian scales. Many traditional Japanese scales are also pentatonic, but they remove different notes, and the result is a completely different world of sound. Keep “which two notes were removed” as the axis of comparison going in.

▶ Play the pentatonic scales in the scale dictionary Switch between major pentatonic, minor pentatonic, and blues and watch the keyboard highlighting. The gaps where notes have been removed are visible at a glance Scale Dictionary → ▶ Run Amazing Grace through a pentatonic scale This tune is generally held to be pentatonic already. Converting it and hearing how little changes is a good way to confirm that Scale Converter →