Blues scales: minor blues, major blues, hexatonic forms and blue notes

Blue notes

African American blues arises from an intonation that does not coincide with equal temperament: the third, the seventh and the fifth are often sung or played “in between” (between b3 and 3, between b7 and 7, between 4 and 5). These blue notes are the heart of the language; the blues scales are their tempered approximation. On guitar they are obtained with bends (often a quarter tone on the b3), on piano with grace notes (acciaccature, b3 → 3).

Minor blues scale (hexatonic)

Degrees: 1 b3 4 b5 5 b7. Steps: 1½ T S S 1½ T.
On A: A C D Eb E G. On E: E G A Bb B D. On C: C Eb F Gb G Bb.
It is the minor pentatonic with the b5 added as a chromatic passing note (D – Eb – E in A). The b5 is also called the “blue fifth”.

Major blues scale (hexatonic)

Degrees: 1 2 b3 3 5 6. Steps: T S S 1½ T 1½.
On C: C D Eb E G A. On A: A B C C# E F#. On G: G A Bb B D E.
It is the major pentatonic with the b3 added that slides to the 3 (Eb – E). A “country-blues” sound, gospel, soul, the “sweet side” of B.B. King and the Allman Brothers.

Note: the C major blues scale contains the same notes as the A minor blues scale (relatives), like the pentatonic scales.

The “complete” blues scale (heptatonic and beyond)

Many texts combine the two: 1 2 b3 3 4 b5 5 6 b7 (nine notes), the complete vocabulary of the blues guitarist. In practice musicians alternate “major” phrases (with 3 and 6) and “minor” phrases (with b3, b5, b7) over the same dominant chord.

How it is used over the 12-bar blues

The minor blues scale of the tonic works over all three chords (I7, IV7, V7). The b3 over a major chord creates the b3/3 conflict, which is the essence of the blues.
The major blues scale works well over the I7 but requires care over the IV7 (the 3 of the tonic becomes the major 7th of the IV: E over F7 grates). Solution: over the IV, switch to the minor or major blues scale of the IV.
Typical phrases: b3 → 3 bend (or to the middle), b5 → 5 slide, b7 → 1 resolution over the I.

Chords and harmony

The blues scale does not “generate” useful diatonic chords: it is a melodic scale over the dominant harmony of the blues (see “The blues: 12-bar form and harmony”). In rock, riffs built on the blues scale are often played as parallel power chords (I5 – bIII5 – IV5 – bV5 – IV5).

Examples in real pieces

“Smoke on the Water” (Deep Purple): the riff in G uses G – Bb – C – Db – C: the Db is the b5 of the blues scale.
“Sunshine of Your Love” (Cream): riff in D with the b5 (Ab) as a passing note.
“Crossroads” (Cream, from Robert Johnson): Eric Clapton’s solos in A minor blues.
“Purple Haze” (Jimi Hendrix): riff and voicings on the E minor blues scale.
“The Thrill Is Gone” (B.B. King): minor blues in B minor, with phrases alternating minor and major.
“Billie’s Bounce” (Charlie Parker): bebop over a blues in F, with blues phrases set among the chromatic lines.

Use in modern production

Hip hop and trap: blues guitar and piano samples, vocal melodies with the “blue” b3 and b7.
Rock and metal: riffs based on the minor blues scale with b5.
Neo-soul and R&B: vocal runs that mix major and minor blues.
Pitch bend: to imitate blue notes on synths and samplers use a pitch bend range of 2 semitones and bend the b3 by about 25–50 cents toward the 3.

Common mistakes

Using the b5 as a held arrival note: it is a passing or tension note.
Correcting a voice’s blue notes with Auto-Tune: you lose the blues. Use a slow retune or turn correction off on those notes.
Playing the minor blues scale over a major pop piece with maj7 chords: the b3 and b7 clash with the major 3 and 7 without the blues context.

Exercise

12-bar blues in A at 90 BPM (A7 D7 E7): improvise using only A minor blues, then only A major blues, then alternating.
Program a “Smoke on the Water”-style riff in E using the b5 (Bb).
On a synth lead, create a phrase with a pitch bend from C to C# (b3 → 3) over an A7 chord.

Pentatonic scales and the blues scale; Pentatonic scales: major, minor and the five modes; The blues: 12-bar form and harmony; Mixolydian mode; Bebop scales.