Blues

The notes

B D E F F♯ A, then B. The F is the blue note between the fourth and fifth degrees, played through rather than held.

The scale contains D against a B7 chord that contains D♯. That friction between the minor third of the line and the major third of the harmony is the whole sound of the idiom.

On the fretboard

Seventh fret with the root on the low E string — the same box as every other blues scale, moved. It also sits at the second fret with the root on the A string, where the open B string can be used as a drone.

That open B is the difference from most other keys: the tonic is available without fretting, so phrases can end on a ringing string rather than a bent one.

Where it is used

Blues and rock in B, and over the V chord in a blues in E — which is where most guitarists actually meet it, without thinking of B as a key at all.

It is also common in seven-string and baritone playing, where B is the lowest available note and the scale sits at the bottom of the instrument.

The key also sits at the boundary of the guitar’s comfortable range. Below B the standard-tuned instrument runs out of notes, so blues written here tends to use the whole neck rather than one box — a practical difference from the same scale played in A or G.