midicnTheory 中文
Pentatonic ScaleChromatic ScaleConsonance and DissonanceAugmented and Diminished Intervals

The blues scale can be defined in one line: the minor pentatonic, plus a lowered fifth.

minor pentatonic (C): C E♭ F G B♭ blues scale (C): C E♭ F G♭ G B♭

The added G♭ (the lowered fifth) is the "blue note", and it behaves in a special way: it is not a stable scale degree but a passing note that has to be slid into and out of. Players move back and forth between G♭ and G, or bend it on a long note. That small pitch instability is the heart of the blues sound — and the reason it cannot be fully written down in equal temperament.

Three structural points

PointExplanation
It has six notes"Pentatonic plus one" adds up to six; notation usually writes five plus an accidental
Lowered and perfect fifth coexistG♭ and G both belong, standing to each other as a diminished fifth / augmented fourth (see [[concept:augmented-diminished
It carries built-in tensionThe lowered fifth is one of the least settled notes available, which is exactly where the gritty blues colour comes from (see [[concept:consonance

The major blues scale

A companion form is often mentioned alongside: the major blues scale — the major pentatonic plus a lowered third. It keeps the same logic (lower one note to create a clash) but on a major base, which reads as a mix of cheerful and mischievous.

Diagram: five notes plus one

The inserted lowered fifth sits alongside the perfect fifth — that clash is the blue note CE♭F GB♭C minor pentatonic CE♭F G♭GB♭ C blues scale G♭ to G is only a semitone — the two fifths compete Performance: slide between G♭ and G, or sing G♭ slightly flat — that drift cannot be fully notated

Listen: before and after the lowered fifth

Hear the minor pentatonic (round, stable), then the blues scale. The added note roughens the colour at once.

Common misconceptions

Listen in the library

Beth Cohen BluesC11:04Folk material titled Blues — hear how the scale actually moves in a melodyDetailsTipperary BluesC11:40Also titled for the blues, on a different instrument — the same scale handled on pianoDetailsWinnsboro Cotton Mill BluesC19:51A longer work in a blues idiom — hear that lowered fifth being stressed over a whole pieceDetails

All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).

Sources

  • 蓝调音阶 = 小调五声音阶加降五度音（"蓝调音"），属通行乐理与流行音乐教材表述
  • 蓝调音在演唱与演奏中常做微分音滑移，为民族音乐学与爵士研究通行表述

Used for fact-checking only; all prose is original.