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Fig. 1 · A# diminished (half–whole) · first 12 frets

guitar scale

A♯ diminished (half–whole)

A♯1B♭2C♯♭3C𝄪3D𝄪♯4E♯5F𝄪6G♯♭7

The same eight notes started a half step earlier: the scale that spells a dominant seventh with a flat ninth and a sharp ninth at once.

The same sounds spelled from the other side are B♭ diminished (half–whole).

on ukuleleon piano

Written out

Fig. 2 · A# diminished (half–whole), ascending

Every accidental is written in, rather than left to a key signature, so the letters can be read one at a time.

The step pattern

A♯HBWC♯HC𝄪WD𝄪HE♯WF𝄪HG♯WA♯

What is true of it

A♯ diminished (half–whole) is A♯, B, C♯, C𝄪, D𝄪, E♯, F𝄪 and G♯, and back to A♯.

Its steps are H – W – H – W – H – W – H – W, where W is a whole step and H a half.

Written correctly it needs 10 alterations, C𝄪, D𝄪 and F𝄪 among them. That is what the letters force, and it is also why nobody writes music in this key: the same notes spelled from the other side are easier to read.

Across the first twelve frets of the guitar its notes fall in 53 places, which is what makes a scale a shape rather than a list.

Chords made only of these notes

C♯majorC♯mminorC♯dimdiminishedC♯7dominant seventhC♯m7minor seventhC♯m7♭5half-diminished seventhG♯dimdiminishedA♯major

Found by testing every chord in the catalogue against these 8 sounds, not chosen.

Other scales on A♯

A♯ whole tonesymmetricA♯ diminished (whole–half)symmetricA♯ majormajorA♯ natural minorminorA♯ harmonic minorminor

C dim H-WC♯ dim H-WD♭ dim H-WD dim H-WD♯ dim H-WE♭ dim H-WE dim H-WF dim H-Wall 374