piano scale
G Mixolydian
G1A2B3C4D5E6F♭7
Major with a flattened seventh: the scale that fits a dominant seventh chord without altering it.
Written out
Every accidental is written in, rather than left to a key signature, so the letters can be read one at a time.
The step pattern
GWAWBHCWDWEHFWG
What is true of it
G Mixolydian is G, A, B, C, D, E and F, and back to G.
Its steps are W – W – H – W – W – H – W, where W is a whole step and H a half.
It uses no sharps and no flats at all: seven letters, seven white keys.
On the same tonic, G major differs from it by exactly one note.
Chords made only of these notes
Found by testing every chord in the catalogue against these 7 sounds, not chosen.