Blues

The notes

A C D E♭ E G, then A. The E♭ is the blue note, sitting between the fourth and fifth degrees; it works as a passing tone or as the destination of a bend, rarely as a held note.

The scale contains C against an A7 chord that contains C♯. That friction between the minor third of the melody and the major third of the harmony is what makes blues sound like blues.

The scale is deliberately incomplete. Six notes leave gaps where the ear expects steps, and those gaps are where bends and slides live — which is why blues played strictly in time and in tune stops sounding like blues.

On the fretboard

The fifth-fret box with the root on the low E string is the single most-played shape on the electric guitar. It sits where the neck is comfortable and where bends are easiest.

Because the tonic is fretted rather than open, every note in the scale can be bent — an advantage the E position does not have, and one reason so many solos are played here even in other keys.

Where it is used

Blues and rock in A, which covers an enormous share of the repertoire. The same shape moved three frets down gives G, two frets up gives B — the box is the method.

It is also the first thing most guitarists improvise with, and the reason a beginner can sound plausible over a twelve-bar within a week of starting.