piano scale
A Lydian
A1B2C♯3D♯♯4E5F♯6G♯7
Major with a raised fourth. The fourth mode of the major scale.
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
AWBWC♯WD♯HEWF♯WG♯HA
What is true of it
A Lydian is A, B, C♯, D♯, E, F♯ and G♯, and back to A.
Its steps are W – W – W – H – W – W – H, where W is a whole step and H a half.
On the same tonic, A major differs from it by exactly one note.
Chords made only of these notes
C♯mminorC♯m7minor seventhD♯dimdiminishedD♯m7♭5half-diminished seventhEmajorEmaj7major seventhF♯mminorF♯m7minor seventh
Found by testing every chord in the catalogue against these 7 sounds, not chosen.