Ultralocrian bb6 Mode on Guitar: Notes, Chords & Examples

The Ultralocrian ♭♭6 mode is one of the darkest, most unstable sounds you can put under your fingers on guitar.

It has a tense, collapsed quality: diminished, chromatic, alien, and almost “wrong” in a useful way. If modes like Phrygian or Locrian sound dark, Ultralocrian ♭♭6 sounds even more extreme.

This is not a casual campfire mode.

It works best for:

Progressive metal riffs
Fusion “outside” lines
Horror soundtrack textures
Diminished chord vamps
Tense transitions and modal modulation
Experimental songwriting

Because of its double-flat intervals, this mode is more advanced than common modes like Dorian or Mixolydian. But on guitar, it becomes very playable once you focus on the sound instead of getting stuck in the spelling.

How does it sound?

Before anything else, let’s hear how it sounds. This can best be done by playing a chord from the mode, and playing the notes of the mode arpeggiated on top of it. This is the best and quickest way to determine the feel of a mode.

This can be quickly done using SLModes, a software dedicated to the music modes, and the following sound was generated by it:

Formula

The interval formula for C Ultralocrian ♭♭6 is:

1 b2 b3 b4 b5 ♭♭6 bb7

Using interval names:

P1 m2 m3 d4 d5 d6 d7

That gives the mode this highly compressed, diminished sound.

The most important color tones are:

b2 — immediate tension
b4 — enharmonically sounds like a major 3rd, but functions differently
b5 — diminished/tritone instability
♭♭6 — enharmonically sounds like a perfect 5th
bb7 — enharmonically sounds like a major 6th

This is why the mode can feel both diminished and strangely “split” between minor, dominant, and altered colors.

Notes in C

The correctly spelled notes in C Ultralocrian ♭♭6 are:

C Db Eb Fb Gb Abb Bbb

For guitar players, the enharmonic pitch names are often easier to visualize:

C Db Eb E Gb G A

Important note:

Fb sounds like E
Abb sounds like G
Bbb sounds like A

So while the theoretical spelling is:

C Db Eb Fb Gb Abb Bbb

Your fretboard shape will look like:

C Db Eb E Gb G A

Both are useful. Use the formal spelling for theory and chord naming. Use the enharmonic notes for finding the mode quickly on guitar.

The Chord That Defines the Mode

The defining chord of C Ultralocrian ♭♭6 is:

Cdim7

Spelled from the mode:

C Eb Gb Bbb

That gives you:

1 b3 b5 bb7

This chord captures the core personality of the mode because it contains the root, minor 3rd, diminished 5th, and diminished 7th. In other words, it gives you the fully diminished sound at the center of the mode.

A fuller modal chord would be:

Cdim7(b9, b11, bb13)

Using the mode tones:

C Eb Gb Bbb Db Fb Abb

But that is very dense and dissonant. For practical guitar use, start with Cdim7, then add color tones like Db, Fb/E, or Abb/G as melodic or riff notes.

A simple Cdim7 guitar voicing:

E|---x---
B|---4--- Eb
G|---2--- Bbb/A
D|---4--- Gb
A|---3--- C
E|---x---

This chord immediately gives you the tense, symmetrical, unstable sound that makes the mode useful.

Chord Progression (Example)

Because C Ultralocrian ♭♭6 is so unstable, it usually works better as a vamp, riff environment, or outside color than as a traditional functional chord progression.

Roman numerals:

i°7 - bII° - i°7 - bIII°

Chords in C:

Cdim7 - Dbdim - Cdim7 - Ebdim

Mood:

This progression sounds claustrophobic, tense, and cinematic. The half-step movement from Cdim7 to Dbdim emphasizes the b2, which is one of the most aggressive notes in the mode.

Use this for:

Horror-style riffs
Dissonant prog interludes
Fusion outside vamps
Tension before resolving into C minor or another darker key

Guitar Fretboard Shape

Here’s the mode mapped across the full fretboard, generated with my software SLModes.

The diagram shows every occurrence of the mode across the neck:

🟢 Green dots = the root note, your anchor points
🟠 Orange dots = the rest of the scale tones

Why Guitarists Love This Mode

C Ultralocrian ♭♭6 sounds dark, unstable, and dangerous.

It does not have the familiar sadness of Aeolian or the exotic darkness of Phrygian. Instead, it feels more abstract and dissonant.

The emotional character is closer to:

Horror
Anxiety
Suspense
Mechanical aggression
Alien landscapes
“Something is about to break” tension

That makes it very useful for modern progressive writing.

Genres Where It Works Well

C Ultralocrian ♭♭6 fits especially well in:

Progressive metal
Technical death metal
Fusion
Experimental rock
Horror scoring
Dark ambient guitar music
Avant-garde jazz
Cinematic instrumental music

It is probably not the first choice for blues, pop, country, or classic rock unless you want a deliberately strange passing color.

Tips for Practicing

To practice a mode effectively, you only need two things:

An instrument to play the mode (your guitar is ready to go!)
A backing track that provides a harmonic context

The fretboard diagram above already show you where the notes are. The remaining piece is choosing an appropriate backing track to improvise over.

Practice with a drone

The simplest option is a single C drone.

You can create one using:

A looper pedal
A synth drone
A sustained bass note in your DAW
An open C tuning
Or any other source of a continuous C note

Because the accompaniment consists of only a single note, you are responsible for highlighting the intervals that define the mode. The more intentionally you emphasize its characteristic tones, the more clearly the modal sound will emerge.

Create modal vamps with SLModes

While a drone is an excellent way to hear a mode in isolation, a modal vamp often provides a more musical and rewarding practice experience.

A well-designed backing track naturally emphasizes the mode’s characteristic intervals, allowing you to focus on phrasing, melody, and expression instead of constantly trying to establish the modal sound yourself. As a result, improvising in the character of the mode often feels more intuitive.

There are many ways to build modal backing tracks, but SLModes can generate them for you in just a few clicks. For example:

Arpeggiated backing tracks — a repeating pattern that outlines every note of the mode.
Chord vamps — progressions built from chords that best reinforce the mode’s unique character.

This video shows you an example: