About tritone.
Which is An interval composed of three whole tones.
This interval was frequently avoided in medieval ecclesiastical singing because of its dissonant quality.
nicknamed the diabolus in musica ("the Devil in music").
"Because of that original symbolic association with the devil and its avoidance, this interval came to be heard in Western cultural convention as suggesting an "evil" connotative meaning in music. Today the interval continues to suggest an "oppressive", "scary", or "evil" sound."
About tritone. Which is An interval composed of three whole tones. This interval was frequently avoided in medieval ecclesiastical singing because of its dissonant quality. nicknamed the diabolus in musica ("the Devil in music"). "Because of that original symbolic association with the devil and its avoidance, this interval came to be heard in Western cultural convention as suggesting an "evil" connotative meaning in music. Today the interval continues to suggest an "oppressive", "scary", or "evil" sound."
http://en.wikipedia.org/wiki/Tritone#Historical_uses