For heptatonic scales, they are mainly meant to be written with all seven letters and the accidentals to them. For example, the C altered scale would have an Fb instead of E because the note is a diminished fourth. However, is there a fixed, accepted way to spell non-heptatonic scales? For the whole-half diminished scale, which is octatonic, there has to be one letter which is repeated with two different accidentals. For the C diminished scale for example, I would presume that note to be B, as the C diminished seventh chord calls for a B double flat, and the scale continues to B natural. However, when you take the half-whole diminished scale starting on D as a mode of C whole-half with the same spelling, it causes a contradiction. The B natural of the C whole-half scale contradicts with D half-whole, which, when constructing a diminished seventh, would require the B natural be called C flat. This means that two scales which are modes of each other have to be spelled differently to be spelled correctly. This contradiction holds for hexatonic scales. I was wondering if there is an accepted rule for this, or if it is just up to the person who writes the music.


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