Originally Posted by: hsnoeckx

A tritone is not the most dissonant sound there is; an augmented fourth ( or likewise a diminished fifth ) is the most dissonant and in the dark centuries it was seen as the Devil's interval and was absolutely forbidden by the church to use in music.

An augmented fourth would be like C to F# ( or Gb ).

Herman

A [u]tri[/u]tone is an interval that spans 3 tones (6 semi-tones = 6 frets on a guitar). So as per your example, C to F#, you have 3 tones (C to D, D to E, E to F#). It's the same as an augmented 4th or diminished 5th. [there may or may not be some intricacies regarding different intonation/temperment systems and so forth, which I know next to nothing about, but for all intents and purposes....].

The story about the tritone being forbidden by the church is a great story. I'd love for it to be true, but it's at least debateable according to most articles I've looked at (e.g., this one).