Which key signatures to use for diminished/augmented scales?

Question

This is more of a music theory question, but I'm working on a music application, and I've been wondering which key signatures I should be using for non-Major and Minor scales. For instance, Diminished, Phrygian, etc...

My gut feeling is to stick with the major key signatures unless the scale is minor-ish, but I'll admit that I'm a little lost...

Any ideas?

Answer 1

For the various modes it is customary to use the signature of the corresponding Ionian (major).

In other words, all the following scale share the same signature (i.e. without any sharp or flat):

• C major
• D dorian
• E phrygian
• F lydian
• G mixolydian
• A minor
• B locrian