F Locrian Mode: Building It From F Minor, One Flat at a Time

What do you get if you take F minor and lower two more of its notes by a half step? You get F Locrian, the darkest and least settled of the seven modes. A mode is simply a scale built by starting on a different note of a familiar scale. Locrian is the one most musicians hear about last and use least, and that's exactly why it's worth understanding. Once you can hear what those two lowered notes do, you'll recognize this sound in metal riffs, in film tension cues and in plenty of jazz.

Start With F Minor You Already Know

F natural minor runs F, G, Ab, Bb, C, Db, Eb. Sing it or play it on a keyboard and you'll hear a sad but stable scale. It feels like it has a home, and F is that home.

Now make two changes. Lower the second note, G, by a half step to Gb. A half step is the smallest step in Western music, like moving from one piano key to the very next one, black or white. Then lower the fifth note, C, by a half step to Cb. That gives you F Locrian:

F, Gb, Ab, Bb, Cb, Db, Eb

Those two changes are the whole story. The lowered second, Gb, sits uncomfortably close to the root, right on top of it. The lowered fifth, Cb, is the bigger deal, and we'll come back to it.

Why Cb and Gb, Not B and F#?

Seeing Cb for the first time can feel like someone is playing a trick on you. Relax: on a piano, Cb is the same key you'd normally call B. So why not just write B?

Scales follow a simple spelling rule: each letter from A to G appears once, in order. F Locrian needs a letter G, a letter C and so on. The note one step above Bb has to be some kind of C, and since we want the note a half step above Bb, it's Cb. Likewise, the second note must be some kind of G, so it's Gb rather than F#. Spell it any other way and you'd end up with two Bs and no C, which makes the music harder to read, not easier.

You could also call this scale E# Locrian. It sounds identical, but it needs 6 sharps and some awkward spellings, so F Locrian is the friendlier name.

The Step Pattern and the Key Signature

Every mode has its own pattern of whole steps (W, two half steps) and half steps (H). Locrian's is H - W - W - H - W - W - W. Walk it up from F:

• F to Gb: half step
• Gb to Ab: whole step
• Ab to Bb: whole step
• Bb to Cb: half step
• Cb to Db: whole step
• Db to Eb: whole step
• Eb to F: whole step

Look closely at those notes and you'll see they're exactly the notes of Gb major (Gb, Ab, Bb, Cb, Db, Eb, F), just started on F instead of Gb. Gb major is called the parent scale, and it gives F Locrian its key signature of 6 flats. The same notes also make up Eb minor, the relative minor of Gb major. What separates F Locrian from those keys isn't the notes but where the music settles: here, everything treats F as home.

The Note That Gives It Away: Cb

In formula terms, F Locrian is 1, b2, b3, 4, b5, b6, b7. Most scales have a perfect fifth, the strong, open interval from F up to C that anchors a key. Locrian replaces it with a diminished fifth, F up to Cb, a tense, hollow interval often called the tritone.

That one note is why Locrian feels unstable. Play F and Cb together on a keyboard and listen. It doesn't sound wrong, exactly, but it sounds like a question with no answer. Cb is the characteristic note of this mode, so when you write in F Locrian, lean on it.

The Chords It Produces

Stack every other note of the scale and you get these chords:

• i°: Fdim (F-Ab-Cb) / Fm7b5
• bII: Gb (Gb-Bb-Db) / Gbmaj7
• biii: Abm (Ab-Cb-Eb) / Abm7
• iv: Bbm (Bb-Db-F) / Bbm7
• bV: Cb (Cb-Eb-Gb) / Cbmaj7
• bVI: Db (Db-F-Ab) / Db7
• bvii: Ebm (Eb-Gb-Bb) / Ebm7

The home chord is diminished, built on that flat fifth, so it never quite feels at rest. That's the main reason whole songs in Locrian are rare. The real challenge is keeping F as home, because Gb and Ebm are strong chords that want to take over and turn the music into Gb major or Eb minor.

Try this progression, slowly, two beats per chord: Fm7b5 - Gbmaj7 - Ebm7 - Fm7b5. The Gbmaj7 sits a half step above home and slides back down; the Ebm7 approaches F from a whole step below. Both keep pointing at F.

Jazz musicians meet this mode constantly in another way: whenever an m7b5 chord appears, Locrian is a natural scale choice over it. Fm7b5, for instance, often shows up as the ii chord in Eb minor.

How a Melody Behaves Here

Locrian melodies tend to hover and creep rather than soar. The Gb wants to sink back to F by a half step, and that tiny drop is the most Locrian gesture there is. The Cb tends to fall to Bb. Singers will find the F to Cb leap tricky at first; practice it slowly against a held F until your ear trusts it.

Keep returning to F, and keep the melody short and repetitive so the listener hears F as the center. Heavy metal guitarists use this approach on low, chugging riffs built around the root, flat second and flat fifth.

For Guitarists

On a standard-tuned guitar, find F on the low E string at fret 1 or 13, or on the A string at fret 8 or 20. Play a palm-muted riff from the 1st-fret F: alternate the open-position F with Gb one fret up, then hit Cb (the same fret as B, fret 2 on the A string). That half-step grind and the tritone will tell you instantly what Locrian is about.

Here's something to try today: hold a low F on piano, guitar or a drone app, and sing or play F - Gb - F - Cb - Bb - F, over and over, until the Cb stops sounding like a mistake and starts sounding like a color.

For the bigger picture, read The Locrian Mode.