You’ve experienced it from a variety of musicians and you’ve heard the phrase batted around as if everyone knows just what it is. But do they? Do you? Here’s what our culture assumes you to already know about the blues scale.
There’s no clear-cut definition what is or is not a blues scale other than it is a scale that can be used to create solos in the wide variety of music known as blues. However, most musicians agree that the six-note blues scale is a good starting point. This blues scale consists of the five-note minor pentatonic scale (”pentatonic” meaning 5 notes) plus one note often referred to as the blue note. Since Western music recognizes 12 major keys and thus 12 minor keys, one for each note in an octave, you can create 12 of these six-note blues scales, one for each key.
The minor pentatonic scale consists of five notes carved out of the seven-note natural minor scale. Note there is more than one “minor” scale, but the blues is based on the natural minor. These five notes are the 1st, 3rd, 4th, 5th, and 7th notes of the natural minor scale (1 being the root note of the scale, the note that names the scale). The sixth note, the blue note that turns this minor pentatonic scale into the blues scale, is the flatted 5th note of the natural minor scale. So, in order, the blues scale is made up of the following six natural minor scale notes: 1, 3, 4, 5-flat, 5, and 7. Here is an example in the key of C minor.
The C natural minor scale is:
C D Eb F G Ab Bb
The C minor pentatonic is
C — Eb F G — Bb
The C blues scale, adding the flatted 5th (Gb), is
C — Eb F Gb G — Bb
But don’t try to put blues in a box, it won’t stay there. Blues is more about how you play the notes, less about what notes you play.
Interesting side fact: the so-called blue note is an interval from the root known as a tritone, which is an interval of three full tones. The tritone has a particularly dissonant, foreboding and unstable sound that lends itself nicely to blues music. Try it on a piano keyboard: in the key of F play root F and tritone B alternatively and listen for the dissonance. In medieval western music, this sinister interval was avoided or purposely used for effect, and often referred to as diabolus in musica (“the Devil in music”). In modern times, this sonic uneasiness has been a staple of dramatic film and TV music, heavy metal, and of course the blues.