Blues scale

Start with A minor pentatonic (A C D E G) and slip one note between D and E: Eb. That is the A blues scale, scale steps 1 b3 4 b5 5 b7.

The flat 5th sits a half step from both of its neighbors and a tritone, an interval of six semitones, above the home note, so it sounds tense on purpose. Players rarely park on it. They slide through it, D to Eb to E, or hammer from Eb onto E, and that quick smear is a big part of what people mean by “bluesy”. Hold the Eb over an A chord for a whole bar and it starts to sound like a wrong note.

“Blue note” is the wider idea. Blues singers and players often pitch the 3rd, 5th and 7th of the scale lower than a piano would, sometimes landing between two keys, and any of those notes can be called a blue note. The blues scale is the keyboard’s version of that sound: a piano cannot play the in-between pitches, so the scale uses the flat 3rd, flat 5th and flat 7th instead.

There is a major version too: the major pentatonic plus a flat 3rd, C D Eb E G A in C. It uses the same six notes as A blues, but with C as home it sounds brighter and friendlier. When people say “blues scale” with no qualifier, they mean the minor one.

Most beginners meet it over the 12-bar blues, number 7 in the most common chord progressions. In A, that form runs on A7, D7 and E7, and the A blues scale works over all three, so one set of notes carries you through the whole form.

Gelato Synth has Blues among the nine scales in Notes mode, and Gelato Chord includes it among its ten. To see where the scale comes from, read why the pentatonic scale sounds good.