Blues Scale

The blues scale is the minor pentatonic scale with one note added — the flatted fifth, called the "blue note." That one extra note is responsible for the signature tension and expressiveness that defines blues phrasing. You can bend into it, slide out of it, and use it to connect the fourth and fifth scale degrees in ways that sound mournful and vocal.

Construction

Start with the minor pentatonic:
A minor pentatonic: A C D E G

Add the ♭5 (blue note):
A blues scale: A C D E♭ E G

Formula: 1  ♭3  4  ♭5  5  ♭7

Step pattern: m3 - W - H - H - m3 - W

The blue note sits between the 4th and the 5th — it's the tritone above the root. It's the most dissonant interval possible in the octave, which is exactly why it sounds so expressive over a blues chord progression. Tension, then release.

Key Blues Scales

E blues scale: E G A B♭ B D E
A blues scale: A C D E♭ E G A
G blues scale: G B♭ C D♭ D F G
B♭ blues scale: B♭ D♭ E♭ E F A♭ B♭

The Blue Note in Context

The ♭5 is usually a passing tone — you land on it briefly as you move through the scale, not a place to sit and sustain. Bending the 4th up toward the ♭5, or sliding from the ♭5 up to the 5th — these are the signature moves. The ♭5 note itself over a I7 chord (A♭ over A7, for example) is a tritone clash with the 3rd (C#) — massively dissonant, immediately resolved by moving to the 5th (E) or back to the 4th (D). That moment of dissonance and resolution is the blues sound.

Blues Scale vs. Minor Pentatonic

Most blues players don't use the blues scale exclusively — they blend the blues scale, the minor pentatonic, and the major pentatonic depending on the moment. When the I chord is a major or dominant seventh (as it is in the 12-bar blues), you can get away with mixing major and minor thirds. B.B. King was a master of this: bending the minor third toward the major third over a major chord creates a tension that's neither fully major nor minor, which is the essence of blues expression.

Where It Comes From

The blue notes in blues music — the ♭3, ♭5, and ♭7 — reflect the collision of African musical traditions (which used different pitch relationships than European equal temperament) with European harmonic structures. The tension between the minor-flavoured melody and the major or dominant harmony underneath is not an error — it's the point. That ambiguity between major and minor is what gives blues its emotional complexity.