interval
G♯ augmented fourth
G♯lowerC𝄪upperA46 half steps
A perfect fourth widened by a half step. Same sound as the diminished fifth, different letter, different behaviour.
On the keyboard
What is true of it
G♯ up a augmented fourth is C𝄪: 6 half steps, and 4 letters counting both ends.
Turn it upside down — put the G♯ on top — and it becomes a diminished fifth. The two numbers always add to nine, and the two sizes to twelve.
It is a dissonance.
Six half steps can be written two ways: G♯ to C𝄪 is a fourth, G♯ to D is a fifth. They sound the same and behave differently.
Every interval on G♯
G♯ → Aminor second · dissonanceG♯ → A♯major second · dissonanceG♯ → Bminor third · imperfect consonanceG♯ → B♯major third · imperfect consonanceG♯ → C♯perfect fourth · perfect consonanceG♯ → Ddiminished fifth · dissonanceG♯ → D♯perfect fifth · perfect consonanceG♯ → Eminor sixth · imperfect consonanceG♯ → E♯major sixth · imperfect consonanceG♯ → F♯minor seventh · dissonanceG♯ → F𝄪major seventh · dissonance