I'm planning on using a diminished 7th to modulate out of Eb minor and into Eb major. I'm thinking of using this diminished 7th or one of its enharmonic equivalents:
This chord could then resolve to C minor and I could use that as the start of my modulation to Eb major. But, I have run into a bit of a problem. You see, I have been using the key signature of Eb major for the whole piece. And this causes a problem because B°7 makes more sense with the key signature while Cb°7 makes more sense with the key. I have no idea which one to use. Unlike with the key of C minor, the diminished seventh chords only match in audible pitch, not in notation.
So, what if I match with the key signature of Eb major, since that is the key I am modulating to? Well, then I would use B°7 which would be notated like this in the key of Eb minor, regardless of key signature:
B natural, D natural, F, Ab
Not that bad, 2 notes, the fifth and the seventh, wouldn't need accidentals at all and the root and third would only need a natural.
Now what if I match with the key of Eb minor? Well then, I would use Cb°7 which would be notated like this in the key signature of Eb major:
Cb, Ebb, Gbb, Bbbb
Just going crazy with the flats here. I mean, every single note has an accidental, the root has a single flat, the third and fifth have double flats, and the seventh, well it has a triple flat. Triple flats can't be notated in Musescore, so the best I could get is turning the Bbbb into an Ab, and then, well, I don't have a diminished seventh anymore, I have a diminished sixth chord, whatever that means(diminished triad with a sixth on top).
You see what I mean? The diminished seventh that matches with the key signature and the diminished seventh that matches with the key are not one and the same diminished seventh. Of course, I could have D natural be the root instead, giving me D natural, F, Ab, Cb, and resolve it to C minor in first inversion instead of the root position C minor resolution I was looking at before. A vi6 chord though is uncommon compared to other predominant chords and even uncommon compared to root position vi.
So, should I use B°7 to match with the key signature and avoid the triple flat? Or should I use Cb°7, even though with Musescore, I have to notate the seventh as a sixth? Or should I change the root and use D°7 and resolve that to a vi6 chord?