A Ionian ♯5 Scale
A Ionian ♯5 contains 7 notes: A, B, C♯, D, E♯, F♯, G♯. It has 4 sharps: C♯, E♯, F♯, G♯. The step pattern is W–W–H–W+H–H–W–H. It is derived from A Harmonic Minor.
Ionian #5 sounds like a major scale that's been stretched upward. It's lush and dreamy, with an augmented 5th that creates a floating, cinematic quality.
Built as 1 - 2 - 3 - 4 - #5 - 6 - 7, this is the 3rd mode of harmonic minor. It takes the familiar Ionian (major) sound and raises the 5th by a half step, producing an augmented major 7th chord (maj7#5) as the tonic harmony. The #5 adds an unresolved, otherworldly quality to an otherwise bright and consonant scale.
Apply this over maj7#5 chords, which are uncommon but provide a unique floating tension. Use your standard major scale shapes and shift the 5th up one fret. The augmented 5th can sound jarring if overused, so treat it as a color note in jazz voicings and film-score-style passages.