Altered Diminished bb3

Three semitones, three whole tones, one leap

Reading the scale upward reveals a shape unlike any other mode of the family. The first three notes are chromatic neighbours — C, D♭, D — after which the scale opens into three consecutive whole steps to E, G♭ and A♭, then a half step to A, and finally a three-semitone leap back to the octave.

Knowing that outline is worth more than memorising the degree names. A cluster at the bottom, a whole tone run through the middle, and a gap at the top describe what the ear actually hears.

Why every degree carries a flat

The written spelling gives each degree an accidental: flat second, double flat third, flat fourth, flat fifth, flat sixth and double flat seventh. Nothing in the sound requires that, and on a keyboard the double flats simply land on ordinary white and black keys.

The reason is functional rather than acoustic. The mode is the seventh rotation of the Neapolitan minor, so it starts on the parent scale's leading tone, and each note keeps the letter name it had in the parent. Respelling D♭ Neapolitan minor from C is what produces a double flat third and a double flat seventh.

The augmented second is at the very top

All seven modes of this family inherit exactly one augmented second, and each places it differently. Here it falls between the seventh degree and the octave, which is the only position where the interval never appears inside an ascending line — it appears at the moment the line arrives home.

That placement gives the mode its restlessness. A melody can walk almost the whole scale by small steps and still cannot reach the tonic without jumping, so the arrival always sounds abrupt.

Not the altered scale

Searching for anything beginning with the word altered returns the altered scale first, and the two are different: C D♭ E♭ E G♭ A♭ B♭ against C D♭ D E G♭ A♭ A here. Two degrees separate them, the third and the seventh, and the altered scale is by far the more useful of the pair.

The closer relative is altered diminished, the seventh mode of the harmonic minor: C D♭ E♭ E G♭ A♭ A. Exactly one note divides them — that scale has a flat third where this one has a double flat third — and the double flat is what pushes the sound away from any diminished chord.

What it is actually good for

Honesty serves better than invention here: this rotation is catalogued far more often than it is played. No standard repertoire calls for it by name, and the parent scale supplies the harmony that made the family worth building in the first place.

Where it does earn its place is as a source of two sounds at once. The root, flat fourth and flat sixth spell an augmented triad, while the chromatic cluster underneath supplies passing motion, so the mode works as material for a line over an augmented chord rather than as a key to compose in.

Frequently asked questions