Altered Dominant bb3

The altered scale with its third lowered once more

The altered scale is C D♭ E♭ F♭ G♭ A♭ B♭. Dropping its flat third a further half step, to a double flat, produces this mode and leaves the other six degrees untouched — which is exactly what the name records.

Sounding, that double flat third lands on D, the same key as the natural ninth. The scale therefore keeps a flat ninth and a natural ninth side by side while giving up the sharp ninth entirely, and that trade is its whole identity.

Not the same as altered diminished bb3

A mode of the Neapolitan minor carries almost the same name and shares the first five notes: C D♭ D E G♭ A♭. Only the last degree separates the two, and it separates them completely.

That relative ends on a double flat seventh, which leaves an augmented second between the seventh degree and the octave — a melody there cannot walk home. This mode ends on an ordinary flat seventh and steps to the octave by a whole tone, so it never leaps at all. The names are close; the endings are opposite.

The chord underneath

Read as sound, the flat fourth is the major third and the chord is C E G♭ B♭ — a dominant seventh with a flattened fifth. The flat sixth supplies an augmented fifth above it, so both fifths are present just as they are in the neighbouring modes of this family.

What marks this one out among them is the bottom of the scale. Three notes sit in a chromatic row — C, D♭, D — so the flat ninth and the natural ninth are both there, immediately above the root, and a line can slide between them.

The whole tone scale plus the flat ninth

Removing D♭ leaves C D E G♭ A♭ B♭ — six pitches a whole step apart, the whole tone scale. Every mode of the Neapolitan major family is that scale with one note added, and here the added note is the flat ninth.

Its sibling adds the sharp ninth instead, and the pair makes the principle easy to hear. Two modes of the same family, the same six-note core, and the single extra note decides whether the chord leans dark or bright above its root.

What it is actually for

Candour serves better than invention: this rotation is catalogued far more often than it is played, and no standard repertoire calls for it by name. Searching it returns the altered scale first in every language checked, with autocomplete debris behind that.

Where it earns a place is as a source of the chromatic approach at the bottom of a dominant. Holding C7♭5 and walking C, D♭, D underneath the chord is the one thing this mode does that its relatives do not.

Frequently asked questions