The tritone
- C1
- F♯♯4
A tritone is six semitones, from C to F♯. Inverted, with the lower note moved up an octave, it becomes the tritone.
Its short name is TT, and it is also called augmented fourth or diminished fifth. Counted in letters, it spans four letter names, which is why it is written C to F♯ rather than with another name for the same pitch.
The tritone on DADGAD guitar
On DADGAD guitar, the tritone is one fret back, one fret up and four frets up when you cross to the next string, and six frets up along one string.
The shape changes from one pair of strings to another, because the strings of this tuning are not evenly spaced. Instead of one shape to learn, there are three of them.
On the staff
On a treble staff, the two notes are written C and F♯.
The staff shows the two notes one after the other, then together. C to F♯ spans four letter names, which is what the interval's name counts. What you hear is a distance of six semitones.
On the keyboard
A keyboard makes this distance easy to see, where a fretboard hides it. The upper note is six keys along from the lower one, counting black and white keys alike.
C and F♯ on the whole neck
23 notes are marked across six strings.
This diagram marks both notes of the tritone, C and F♯, everywhere they fall on DADGAD guitar. You can find every pair shown above somewhere on it.
A tritone above every note
| From | A tritone up |
|---|---|
| C | F♯ |
| D♭ | G |
| D | G♯ |
| E♭ | A |
| E | A♯ |
| F | B |
| F♯ | B♯ |
| G | C♯ |
| A♭ | D |
| A | D♯ |
| B♭ | E |
| B | E♯ |
C–F♯, D♭–G, D–G♯, E♭–A, E–A♯, F–B, F♯–B♯, G–C♯, A♭–D, A–D♯, B♭–E, B–E♯
The shapes above do not change with the key, which is the reason to learn an interval as a shape. Only the note names change, and this table gives them for every starting note.
Chords built on the tritone
- DiminishedC°
- Half-diminishedCm7♭5
- Diminished 7thC°7
Three chord types contain a tritone: Diminished, Half-diminished, Diminished 7th.
These are the chords with a tritone above their root. Some of them spell that note under another name, but it is the same distance and the same shape on the neck. A chord is built by stacking intervals on a root, and a triad is the simplest case, with two of them.