Locrian bb3 bb7

The bb in the name is not a B flat

Written in plain text, the name reads like a chord: bb3 and bb7 look as though they refer to B♭. They do not. The doubled b is a double flat, and it applies to the third and the seventh degrees of the scale — the third lowered twice and the seventh lowered twice.

The confusion is common enough to be worth stating plainly. This page is about a seven-note scale, not about B♭ chords or B♭7. If you arrived looking for a chord, the catalogue has separate pages for those.

Why the spelling is so heavy

Each mode must use each letter name once, and this one is the seventh mode of a scale that already contains two flattened degrees. Counting up from the parent's seventh degree forces two double flats, and there is no way to write the scale correctly without them.

By sound the scale is simpler than it looks: from C the pitches are C, D♭, D, F, G♭, A♭ and A. The first three notes are consecutive semitones, then a gap of three semitones to F. That opening cluster is what identifies the mode.

What it is used for

The scale has no perfect fifth and no usable third — the doubly flattened third sounds as a major second — so it does not describe a chord in the way the other modes of this family do. It is a colour, and in practice it appears where a composer wants the parent scale's material read from an unexpected centre.

Film and game scoring is where that happens most. Over a drone it produces the tightest cluster the double harmonic family offers, and the ear cannot resolve it to any familiar chord, which is the point.

Where it comes from

The double harmonic scale is 1 ♭2 3 4 5 ♭6 7, catalogued elsewhere as Byzantine, Arabic or Gypsy major. Reading its seven notes from the seventh degree and transposing to C gives this mode, with both of the parent's augmented seconds intact: by sound they fall from D up to F and from A up to the octave, three semitones each.

Among the family's seven modes this is the one least likely to be reached for deliberately. It is catalogued because the family has seven modes and completeness has a value; the pages that get used are the parent, Hungarian minor and the second and sixth modes.

Frequently asked questions