How to notate a non-standard hexatonic key

Question

I am writing part of a piano piece in a hexatonic "key" containing these notes:

C - D# - E - G - Ab - B

(I say "key" instead of scale because I'm treating it like a key, deriving not just melody but also the chords from this "key", and staying mostly "in key". If you think that this is not a key but a scale, feel free to call it a scale in your answer.)

The "key" is the same when transposed up or down a major third, but it makes most sense to see this part as being in some sort of key of C, because it starts with a C minor-ish feel and ends with a C major-ish feel.

Now I'm wondering how to notate this. Do I consider the D# and E to be an Eb and Fb in order to have a key signature with only flats? Or would three flats just confuse people into thinking the part is in Eb? Do I use a novel key signature with a sharp and a flat? Or should I notate this in C and use accidentals for D# and Ab? Maybe there is a precedent?

Answer 1

If you want it to be read and played, use an open key signature and accidentals.

If you want it to be analysed and discussed, maybe concoct a non-standard key signature.

Answer 2

Use accidentals. Do not use a key signature.

Further, do not automatically notate all notes of the 2nd and 5th scale degrees as D# and Ab, respectively. Using Eb and G# might make more sense in certain contexts. (Generally, you should avoid notating augmented intervals.)

I know from experience that this is the best way. I have composed with this scale and countless other scales. While it is initially tempting to use a non-standard key signature in such a case, it is not a good idea. Here are some reasons:

1. Most performers have spent their lives internalizing and optimizing for standard notation and will be tripped up by any non-standard elements. To avoid confusion and performance mistakes, only deviate from standard notation when absolutely necessary. Include explanations of any such deviations with the score. The liberal use of accidentals isn't really a deviation from normal at all and requires no explanation. It is certainly a smaller deviation than a whacky key signature mixing sharps and flats.
2. While a non-standard key signature might technically be feasible for some scales, this is not generally the case for any and all scales. For example, it is impossible to devise a key signature for the octatonic scale. I'm inclined to go with an approach that is more broadly applicable.
3. You might want to use more than one scale in the same composition. Then what, change key signature? What if you're using two scales simultaneously (eg augmented in the left hand, double harmonic in the right)? Then it will get messy. It's best to just use accidentals.

In other words, K.I.S.S.

Answer 3

There's no particular rule for this, so you can go with whatever makes the most sense for your music.

The particular scale you're using is more commonly known as the Augmented Scale and is notated C - Eb - E - G - G# - B. The name comes from the presence of two augmented chords – C, E, G# and Eb, G, B. The scale spelling also clarifies its construction as an interleaved C minor triad and E major triad.

Wikipedia lists several compositions and composers who have employed this scale.

Answer 4

Hexatonic pole of C! I (and plenty other composers among history) used this here and there when composing in a more modal atmosphere. I love the suspensions made by this progression I-bvi-I with pads of sustained chords. There's a traditional association with archetypes of death and sadness/melancholy.

Usually, no key signature and accidentals wherever needed. I prefer to explicit the pole (using C Maj and Ab min triads), but in some passages this enharmonic spelling will be easier to read. In melodic flux, I see no problem on the alternating naturals and flats, but may be confusing to some instrument idioms and, maybe, some performers. If you're not writing having one specific musician in mind, spell the notes in the manner you find more legible and coherent. And, obviously, adhere to this pattern of spelling throughout the entire piece/movement.