The blues scale, in its most common form, has six notes. In C it is C–E♭–F–G♭–G–B♭: the minor pentatonic scale (C–E♭–F–G–B♭) with one extra note, the flattened fifth G♭, squeezed between F and G. The flat third, flat fifth and flat seventh are the scale’s blue notes, which clash deliberately with the major chords of a blues and create its gritty, expressive tension.
Because the scale fits the whole 12-bar blues surprisingly well, beginners often learn it as their first improvising tool, and experienced players use it for quick, punchy phrases within more complex lines. Real blues phrasing goes beyond the written notes, bending pitches and sliding between them. In jazz lo-fi, blues-scale fragments turn up in sampled saxophone riffs, guitar fills and short keyboard licks that answer the main loop.