If you already know the pentatonic minor scale, the blues scale is one note away. That one note — the chromatic passing tone between the 4th and 5th degrees — is what gives blues its grit. It’s the note that separates “playing in a minor key” from “playing blues.” This is Part 4 of the guitar scales blues series, building on the pentatonic foundation from the earlier lessons.

Colin calls it by several names: the flatted fifth, the augmented fourth, the devil’s note, the chromatic pass note. They’re all the same pitch — it just depends on whether you’re going up or coming down.

Where the Blue Note Lives

In the key of A, the pentatonic minor scale gives you five notes: G, A, C, D, E. The blue note sits between D (the 4th) and E (the 5th) — that’s a D#/Eb. It’s technically outside the key, which is why it creates that tension.

The pentatonic scale’s smallest interval is a whole tone. By squeezing this chromatic note in between the 4th and 5th, you create a semitone step — and when you have three notes moving in semitones (D, D#, E), that’s a chromatic run. That’s the blues sound.

Going Up vs Coming Down

When you’re ascending through the scale, the blue note acts as an augmented 4th — you’re raising the D up a half step toward E. When you’re descending, it functions as a flatted 5th — you’re lowering the E down a half step. Same note, slightly different effect on the ear.

The key rule: don’t land on it. The blue note is a passing tone. You move through it on your way to somewhere else. Stopping on it sounds wrong. Sliding through it sounds like blues.

Applying It to the Pentatonic Climb

If you learned the pentatonic climb (the three-position diagonal pattern), you can add the blue note at each position. In the first position, it falls between the 4th and 5th on the same string. In higher positions, you might need to shift your fingering slightly to fit it in.

The blue note also works in the standard A minor pentatonic box position. In box 1 at the 5th fret, the blue note falls on the 5th string, 6th fret — right between D (5th fret) and E (7th fret).

Using It in Chords Too

Colin points out that the chromatic passing tone doesn’t just work for single-note lines. You can use it in chord movements too — walking a chord shape up a fret between the 4th and 5th creates the same bluesy effect. That’s how blues closing riffs work: a chromatic chord walk from the IV up to the V.

It’s one note, but it changes everything. For more on how to make your scales sound darker, check out the dark guitar scales lesson. And for the full blues scale series, see Part 1, Part 2, and Part 3.