The tritone (augmented 4th, diminished 5th) on the guitar
6 semitones · TT · C → F♯
Its character, in the app's words: unease; an octave wider (#11), luminous unease: the instability turns to mystery.
The shapes on the neck
- On the same string: 6 frets up.
- On the next string, towards the 1st: 1 fret up; 2 frets up when you cross from the G string to the B string, which are tuned a major 3rd apart instead of a 4th.
- Turned upside down it becomes a tritone: 6 + 6 = 12 semitones.
The root is the C on the A string, 3rd fret; the other circles are the same note, F♯, wherever it sits between frets 0 and 12. The 1st string (high e) is at the top, as in the app. The root is filled.
Open it in the app: 2. Intervals
The other intervals