Bb locrian

Construction

Step pattern (W = whole step, H = half step): H-W-W-H-W-W-W.

Formula (intervals from the root): 1-b2-b3-4-b5-b6-b7.

Locrian is the darkest diatonic mode -- a minor scale with both b2 and b5. The diminished fifth means even the tonic triad is unstable, making Locrian more of a harmonic color than a functional key center.

Origin and Relationships

Locrian is a mode -- a scale derived by starting a parent scale from a different degree. It belongs to the diatonic modes family as the 7th mode of the major scale.

• Parent: the major scale starting from its 7th degree. To find the parent, go up a half step from the Locrian root.
• Compare to Phrygian: both share b2, but Phrygian has a perfect 5th (stable tonic) where Locrian has b5 (unstable tonic). That single difference is why Phrygian can anchor a key center and Locrian cannot.
• Locrian natural 2 (the 6th mode of melodic minor) raises the b2 to a natural 2, removing Locrian's harshest interval while keeping the b5. It is the more common choice over half-diminished chords in jazz.

Harmonic Context

In Roman numeral analysis (uppercase = major, lowercase = minor):

• i° (fully diminished -- stacked minor thirds): The tonic triad is diminished -- inherently unstable. Locrian struggles to establish a sense of "home" because the root and 5th form a tritone instead of a perfect fifth.
• iø7 (half-diminished -- minor 7th with a b5): More common as a functional chord. In a minor-key ii-V-i progression (a standard chord sequence: half-diminished, dominant, minor tonic), the iiø7 is Locrian's natural territory.
• bII (major): Sits a half step above the root and exerts strong gravitational pull away from Locrian's tonic. The ear often hears bII as the real home.

Characteristic Tones

The intervals that give Locrian its distinctive sound:

• b5 (diminished fifth): The defining Locrian interval. It turns the tonic triad into a diminished chord, removing the perfect-fifth foundation that every other diatonic mode relies on for tonic stability. Compare to Phrygian: where Phrygian's perfect 5th keeps its dark sound anchored, Locrian's b5 lets the ground fall away.
• b2 (minor second): Shared with Phrygian, the b2 adds exotic darkness. But in Locrian, the b5 dominates the character -- the b2 is secondary color.

Melodic Applications

Locrian works best in short bursts or over half-diminished chords rather than as a sustained tonal center. Within a minor ii-V-i, it covers the iiø7 before the line moves through an altered dominant sound over V7 and resolves to the minor tonic -- practicing the full sequence gives Locrian a purposeful trajectory instead of leaving it stranded. As a standalone color, use it for a bar or two of dark tension before resolving elsewhere. Avoid trying to sustain a Locrian tonic; the b5 will constantly pull the listener toward bII.

Practice Seeds

Half-diminished context. Play Locrian over the iiø7 in a minor ii-V-i, then continue through V7 and resolve to i. Experience the mode in its functional home and hear how the full progression gives Locrian direction.

The unstable tonic. Try to sustain a Locrian tonic for eight bars. Feel how the b5 fights stability and the ear drifts toward bII -- understanding this limitation is essential to using the mode well.

Phrygian comparison. Play Phrygian and then Locrian from the same root. Hear how the perfect 5th in Phrygian keeps things grounded while the b5 in Locrian dissolves the foundation -- both have b2, but the 5th degree changes everything.

Passing color. Use Locrian for two to four beats within a longer phrase, then resolve to a stable chord. Practice deploying the mode as a brief, dark tension that makes the resolution more satisfying.