G Locrian Mode: Four Flats, Two Half Steps and a Restless Sound
Why would a scale that starts on G, a note with no sharp or flat of its own, end up needing four flats? That's the first thing most students ask about G Locrian, and the answer explains almost everything about how this mode sounds. Its seven notes are G, Ab, Bb, C, Db, Eb, F. Every one except G, C and F carries a flat, and two of those flats sit right where they make the scale feel like it's leaning off a ledge.
One Letter at a Time
A scale in Western music uses each letter name, A through G, exactly once. That rule is why the spellings come out the way they do. Start on G and walk up the alphabet: G, A, B, C, D, E, F. Now adjust each letter to fit the Locrian sound.
The second note is only a half step above G. A half step is the smallest step in Western music, like moving from one piano key to the very next one, black or white. The key right above G is the black key you could call G# or Ab. Since we've already used the letter G, it has to be Ab. Calling it G# would give us two G's and no A at all.
The same logic gives us Bb for the third note, C for the fourth, and then the big one: Db for the fifth. On a piano, Db is the same key as C#, but we've already got a C, and we need a D. So it's Db. After that come Eb and F, and you're back to G.
If those flat spellings look fussy, don't worry. They aren't there to trip you up. They're there so each note has its own letter, which makes the scale far easier to read and to build chords from.
What the Four Flats Are Telling You
Those flats, Bb, Eb, Ab and Db, are exactly the key signature of Ab major. A key signature is the cluster of sharps or flats written at the start of a piece of sheet music, telling you which notes are altered throughout. Ab major uses four flats, and G Locrian uses the very same notes: Ab, Bb, C, Db, Eb, F, G.
So G Locrian is what you get when you play the Ab major scale but treat G, its seventh note, as home. Musicians call Ab major the parent scale. Same notes, different centre of gravity. A singer reading a chart in four flats might be in Ab major, F minor, or, more rarely, G Locrian. The notes alone don't decide it. What decides it is where the music keeps returning and coming to rest.
Where the Half Steps Fall
The step pattern of Locrian is H - W - W - H - W - W - W. A whole step (W) is two half steps, like skipping one piano key. Applied to G:
- G to Ab: half step
- Ab to Bb: whole step
- Bb to C: whole step
- C to Db: half step
- Db to Eb: whole step
- Eb to F: whole step
- F to G: whole step
Look at where the two half steps land. The first is right at the bottom, G to Ab, so the second note crowds the root. Most scales put more space there; this one sounds hemmed in from the start.
The second half step, C to Db, is the one that changes everything. In most scales the fifth note sits a perfect fifth above the root, seven half steps up, the most stable interval after the octave. Here it's only six half steps up. That shortened fifth, the diminished fifth or flat 5, is Db, and it's the defining note of G Locrian. Play G and Db together on a piano and listen: it's the tense, hollow, slightly sinister interval also known as the tritone.
Chords That Won't Sit Still
Stack every other note of the scale and you get these chords:
- i°: Gdim (G-Bb-Db) / Gm7b5
- bII: Ab (Ab-C-Eb) / Abmaj7
- biii: Bbm (Bb-Db-F) / Bbm7
- iv: Cm (C-Eb-G) / Cm7
- bV: Db (Db-F-Ab) / Dbmaj7
- bVI: Eb (Eb-G-Bb) / Eb7
- bvii: Fm (F-Ab-C) / Fm7
The home chord is Gdim, a diminished triad, because that Db replaces the D you'd expect. A diminished chord sounds like a question, not an answer, which is why Locrian never truly feels at rest. Jazz players know the four-note version, Gm7b5, very well: it's the chord on the second step of F minor, usually heading somewhere else.
To make G feel like home anyway, lean on the Ab chord. That half step from Ab down to G pulls hard. Try this progression, slowly, on piano or any instrument:
Gm7b5 – Abmaj7 – Gm7b5 – Fm7 – Abmaj7 – Gm7b5
Keep G low in the bass on the Gm7b5 bars. You'll hear the Abmaj7 glow briefly, then sink back into that uneasy G. That sinking is the Locrian feeling.
How a Melody Behaves
Melodies in G Locrian tend to hover. Sing or play G, then Ab, then back to G, and you'll hear a sighing, anxious motion. Add Db and the tension climbs. Many melody writers avoid landing on Db for long, using it as a dark passing colour, and keep returning to G, Bb and Ab to anchor the ear.
Because Locrian is so unstable, you'll mostly hear it in short stretches: tense film-score moments, heavy riff-based rock and metal that thrives on that tritone, and passages in jazz built around the m7b5 chord. Few complete songs live in it start to finish; it's more of a mood you visit.
For Guitarists
Your G roots sit on the low E string at frets 3 and 15, and on the A string at frets 10 and 22. Start from the 3rd fret on the low E and play G, then Ab one fret up, then Bb two frets above that. Keep a low G ringing and pick Db on the A string, fret 4, to hear the flat 5 grind against it. Then try the same from the A string at fret 10, where the shape sits comfortably under the hand.
Something to Try
Record yourself holding a low G for a minute. Over it, play or sing only three notes, G, Ab and Db, in any order, ending each phrase on G. Then swap Db for D natural and do it again. That one changed note is the difference between Locrian and everything more settled, and hearing it side by side will fix the sound in your ear for good.
For the bigger picture, read The Locrian Mode.