Lydian Dominant b6

The only mode of its family with a perfect fifth

Stacking thirds from the root gives C E G B♭ — a plain dominant seventh, nothing altered. Among the seven rotations of the Neapolitan major this is the only one whose tonic chord has a perfect fifth; every other mode produces a raised fifth, a flattened fifth or a minor tonic.

That makes it the family's point of contact with ordinary harmony. A player can drop this scale over an unaltered C7 in a normal progression, which is not true of its neighbours, and the alterations then arrive purely as upper-structure colour.

A raised eleventh and a flat thirteenth over a stable chord

Above the C7 the remaining notes fall into place as a natural ninth, a raised eleventh and a flat thirteenth. The combination is unusual: the top of the chord is altered in both directions while the bottom stays completely conventional.

The flat thirteenth sits a half step above the fifth, A♭ against G, and that rub is what a listener actually notices. Leaning on the A♭ darkens the chord instantly; leaving it out reduces the mode to an ordinary Lydian dominant.

One note from Lydian dominant

Lydian dominant from C is C D E F♯ G A B♭, the standard choice over an unaltered dominant with a raised eleventh. Flattening its sixth to A♭ produces this mode and changes nothing else.

For a guitarist that is a single finger. The Lydian dominant shape stays where it is, the sixth degree moves down a fret, and the chord underneath does not have to change at all — which is the cheapest way to hear what the flat thirteenth actually does.

The whole tone scale plus the fifth

Removing G from these seven notes leaves C D E F♯ A♭ B♭ — six pitches a whole step apart, the whole tone scale. Every mode of this family is that scale with one note added, and here the added note is the perfect fifth itself.

That explains the previous section from the other direction. The fifth is exactly what whole tone material lacks, so adding it is what gives this mode a stable chord while its siblings float; the family's odd one out is odd for a structural reason.

Against Mixolydian b6

Mixolydian b6 is the closer-sounding relative and belongs to the melodic minor family: C D E F G A♭ B♭. Only the fourth degree separates them, F against F♯, and both share the flat sixth over a dominant seventh.

Choosing between them is choosing the eleventh. Mixolydian b6 offers a perfect fourth that behaves as a suspension and wants to resolve to the third; this mode offers a raised fourth that behaves as colour and stays put. The flat thirteenth sounds identical in both.

Frequently asked questions