A# Locrian Mode: Building It from the Minor Scale You Know

Think of a suspense cue in a film score: low strings creeping upward, a chord that never quite lands, a melody that keeps leaning on the note just above home as if it wants to escape. That uneasy, hovering quality is the world of the Locrian mode. In A#, the mode uses the notes A#, B, C#, D#, E, F#, G#, and it is the most restless of the seven modes. Its home chord refuses to sit still. That is exactly why composers, jazz players and heavy-music writers reach for it when they want tension instead of comfort.

Start from a scale you already know

The easiest way into A# Locrian is through the natural minor scale, the familiar "sad" scale behind countless ballads. A# natural minor is spelled A#, B#, C#, D#, E#, F#, G#. Sing or play it and it feels dark but settled. It has a clear home.

Now change just two notes:

• Lower the 2nd from B# down to B. The second note now sits only a half step above the root. A half step is the smallest step in Western music, like moving from one piano key to the very next one, black or white.
• Lower the 5th from E# down to E. This is the big one.

That gives you A#, B, C#, D#, E, F#, G#. Two small adjustments, and a moody but stable minor scale turns into something that never feels at rest.

Why that lowered 5th changes everything

The 5th of a scale is its anchor. In most scales, the root and the 5th together form a strong, open sound, the interval called a perfect 5th. Lower that 5th by a half step and you get a diminished 5th, sometimes nicknamed the tritone. It splits the octave exactly in half, and to most ears it sounds tense and unresolved.

In A# Locrian, that note is E. It is the character note of this key, the one that gives the mode its identity. When you hear A# and E together, you are hearing the Locrian sound in a single interval. Try it on a piano: play A# with your left hand and E with your right, and let it ring. It hangs in the air, waiting for something to happen.

The full formula, measured from the root, is 1, b2, b3, 4, b5, b6, b7. In steps, where W is a whole step (two half steps) and H is a half step, the pattern runs H - W - W - H - W - W - W. Starting on A#: a half step to B, whole steps to C# and D#, a half step to E, then whole steps to F#, G# and back to A#.

A word about the spelling

Seeing plain B and E in a scale built on A# can look odd at first, since those are the "lowered" notes yet they carry no flat sign. That is perfectly normal. Lowering B# by a half step gives you B, and lowering E# gives you E. Each letter from A to G appears exactly once, which is the rule that keeps scale spelling tidy.

These notes are shared with B major (B, C#, D#, E, F#, G#, A#), so A# Locrian uses B major's key signature of 5 sharps. Same notes, but the music starts and resolves on A# instead of B.

You may also meet Bb Locrian. It sounds identical, but it needs 7 flats to spell, so A# is usually the friendlier choice on paper. Neither is wrong; they are two names for the same sound.

The chords hiding in the mode

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

• i°: A#dim (A#-C#-E) / A#m7b5
• bII: B (B-D#-F#) / Bmaj7
• biii: C#m (C#-E-G#) / C#m7
• iv: D#m (D#-F#-A#) / D#m7
• bV: E (E-G#-B) / Emaj7
• bVI: F# (F#-A#-C#) / F#7
• bvii: G#m (G#-B-D#) / G#m7

The home chord, A#dim, is a diminished triad, built from two stacked minor 3rds. Its seventh-chord version, A#m7b5, is the "half-diminished" chord jazz musicians use constantly in minor-key ii-V progressions. In Locrian, though, it is home base, which is why the mode feels so unsettled.

The danger is that B major, sitting just a half step up, is so stable that your ear wants to treat it as the real home. To keep the Locrian feeling, keep returning to A#. Try this loop, one bar per chord:

A#m7b5 - Bmaj7 - G#m7 - A#m7b5

Then try swapping in E for a bar to put the character note in the bass: A#dim - E - B - A#dim.

How a melody behaves here

Melodies in A# Locrian tend to creep rather than soar. The B just above the root acts like a heavy neighbor: step up to it and back down to A#, and you get that claustrophobic, sliding sound common in dark film cues and heavy riff-based music.

Let E appear on strong beats when you want the strangeness to show. Land on A# at the ends of phrases. Avoid lingering on a B-D#-F# outline for too long, or the ear will quietly decide you are in B major. Singers will find the half step from A# to B tricky at first; hum it slowly against a held A# until it sits comfortably.

For guitarists

Your root A# sits on the low E string at frets 6 and 18, and on the A string at frets 1 and 13. The 6th-fret position is a comfortable place to start: play A# there, then work up the scale across the strings, keeping your ear on the half step to B and the tritone to E. The 1st-fret A string root is handy for low, grinding riffs that bounce between A# and B.

Something to try

Hold an A# drone on a keyboard or app. Over it, sing or play only three notes: A#, B and E. Make up a four-bar phrase that ends on A#, then another that ends on E. Listen to how differently the two endings leave you feeling.

For the bigger picture, read The Locrian Mode.