Key Signatures

[nekha]

Just wondering... Bb Lydian b7 scale.. would take F minor key signature? or Eb major key signature? or maybe F major key signature?

thanks a lot!

P.S: the tune is a modal vamp in Bb Lydian b7

[Michel]

The Lydian b7 scale ----> Bb C D E F G Ab Bb
Bb C D and E (#4) gives you the Lydian sound
F G Ab (b7) and Bb gives you the V7 sound (Mixolidian)

Now the chord tones
1> Bb
3> D
5> F
7b > Ab

Looks like a V7. So the key signature be Eb. But ...
Those scale best expresses altered dominant scale or m7b5 chords so i dont know if there is a key signature for altered scale that fits altered chords.

[JonR]

Just wondering... Bb Lydian b7 scale.. would take F minor key signature? or Eb major key signature? or maybe F major key signature?

thanks a lot!

P.S: the tune is a modal vamp in Bb Lydian b7

Lydian b7 isn't a key, so has no key signature. Music is not normally written in lydian dominant - which needn't stop you of course. (It WAS used by one or two 20thC composers: Bartok and Kodaly, I believe - who knew it as the "overtone scale".)

The alternatives are as follows, and I think any one could be acceptable (none is either "correct" or "incorrect"):

1. Blank key sig: use accidentals for the Bb and Ab;

2. F major: use accidental for the Ab (probably the most economical in use of signs).

3. Eb major: use accidental for the E natural.

4. Bb major: needs accidentals for both E natural and Ab - so no better than a blank key sig, except it does signal the keynote. (NB: key sigs do NOT normally indicate a keynote, only a scale.)

5. A synthetic key sig consisting of Bb and Ab. This may well have been how those 20thC composers would have indicated it.
You might get some confused looks from conventionally trained readers (who might think it was a mistake for Bb major), but it's a perfectly logical solution. However, any musician with some experience of playing avant garde 20thC classical music shouldn't be thrown.
It should perhaps be accompanied by the phrase "lydian dominant", "lydian b7", or "overtone scale"* at the beginning of the music, to avoid potential confusion.

The scale is a mode of F melodic minor, but an F minor key sig (4 flats) would also need two accidentals, on E and D. I don't see any advantage that offers.


* BTW, "overtone scale" is really a misnomer, as the scale (in equal temperament) doesn't quite line up with the harmonic series. No better than Ionian or Mixolydian anyway.