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As the title suggests. When playing the Dorian flat 2 mode in Ab, the second note would be called a Bbb right?

Avgrundsdjur
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4 Answers4

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Yes, Ab dorian b2 or phrygian ♮6 has notes: Ab Bbb Cb Db Eb F Gb.

Consider that this scale is a second mode of Gb melodic minor. Name Gbm is actually rarely used due to large number of accidentals, F#m is more frequent. If you switched to sharps, you would get G# dorian b2: G# A B C# D# E# F#, so a bit less accidentals. But if you have a good reason to call it Ab scale, then yes, that's correct.

user1079505
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  • Cheers for confirming straight to the point! The real reason for having it as Ab was simply because i played it on a downtuned guitar. Just seemed simpler for the moment of writing but G# is indeed a simpler version ! – Avgrundsdjur Aug 05 '21 at 12:59
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Considering the Dorian ♭2 on C based on the second degree of B♭ minor:

X: 0
K: C
L: 1/4
_B, C _D _E F G A _B
C _D _E F G A _B c

You're correct, as the result is that A♭ it is based on G♭, which actually is B♭♭ major:

X: 1
K: C
L: 1/4
_G _A __B _c _d _e f _g
_A __B _c _d _e f _g _a

But I wouldn't really suggest so. If you can, use the enharmonic G# (based on F# minor).

X: 2
K: C
L: 1/4
^G A B ^c ^d ^e ^f ^g
A B ^c ^d ^e ^f ^g a
Aaron
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musicamante
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Yes.

Technically the B♭♭ is enharmonically equivalent to A natural which is one half step above A♭.

Why, the crazy spelling with a double flat?

Try thinking of it this way: if you numbered the degrees of a scale, each degree would get a separate number. For a seven step scale like the one in questions you would simply number it 1 2 3 4 5 6 7 and then 1 again to repeat at the octave. You wouldn't number it 1 1.5 2 3 4 5 6 then 1 to repeat. Numerically it's correct, all the numbers are unique, but it needlessly obscures there are seven degrees total. You would number it with whole numbers.

The same thing basically happens with letters. Seven letters are used for a seven degree scale. One unique letter is used per scale degree. So, if you start with A♭, the next degree will be some kind of letter B. Of course we have to spell it specifically as B♭♭ to get a tone that is one half step above A♭.

This system starts to break down when using standard staff and scales that don't use seven degrees. Less than seven isn't a big problem. You just need to decide which letters to omit. But, with more than seven degrees, like an octatonic scale, you must repeat a letter.

You can't avoid these issues. Staff notation was developed centuries ago for styles that were much more diatonic, less chromatic.

Michael Curtis
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  • Actually system can break down for 7 note scales already, see e.g. https://music.stackexchange.com/a/116214/63781 or consider modes of harmonic minor, or double harmonic major etc. But at least in this example the "system" holds. – user1079505 Aug 04 '21 at 17:57
  • @user1079505, there is no particular problem with spelling harmonic tetrachords: the gamut `A B C D E F G A`, harmonic minor `A B C D E F G# A`, double harmonic `A Bb C# D E F G# A` – Michael Curtis Aug 04 '21 at 19:49
  • Yes, but consider e.g. 2nd mode of double harmonic scale. You end up with #6 and 7, which may look good on paper, but I guess most people would hear it as b7 and 7. Also see the superlocrian example I linked above. – user1079505 Aug 04 '21 at 20:03
  • Just figure out how to spell the intervals properly, then you can transpose it. Harmonic minor `A Bb C# D E F G# A`, its second mode `Bb C# D E F G# A Bb`, if for some reason you want to take that mode, treat it like a bona fide scale, making `Bb` the "tonic", the intervals above the tonic are `R A2 M3 A4 P5 A6 M7 R`, transposed to `B` it's `B Cx D# E# F# Gx A# B`. Yes, that's an awful bunch of enharmonic names. But you also have to question whether that's a bona fide scale. Playing mode of/rotations of a scale doesn't necessarily make new tonalities. – Michael Curtis Aug 04 '21 at 20:23
  • If you were given this bunch of notated tones `B Cx D# E# F# Gx A# B`, which Wikipedia unconvincingly calls the "Lydian ♯2 ♯6" scale, it might make much more sense to say `B` is actually _not_ a tonic, and it could be enharmonically respelled as double harmonic with tonic `Bb` as `Bb Cb D Eb F Gb A Bb`. You can find real music with the double harmonic scale on the tonic. I don't any music actually in the "Lydian ♯2 ♯6" mode. – Michael Curtis Aug 04 '21 at 20:34
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So the second degree of A is Bb, now in the Phrygian Ab scale all degrees have to be flattened! - and Bb becomes Bbb, yes.

Albrecht Hügli
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