The Devil in Music - we can't live without it!

A musical interval that spans three whole tones is called a tritone (three + tone).  The interval created by three whole tones is an augmented 4th.  It may also be recognized as a diminished 5th.  Whatever the name, this interval is dissonant in the extreme.  Church practice during the Middle Ages banned the use of this dissonant interval.  They called it “diabolus in musica”…. The devil in music.

But those church leaders were tilting at windmills.  The tritone appears naturally in music.  It can be found on the diatonic scale between the 4th and 7th degrees.  On a G-scale the tritone appears between C and F#.  On a D-scale the tritone appears between the G and the C#.   

The interval lies within the dominant 7 chords, too.  At the end of a phrase, in the key of G, the music frequently calls for a D7 chord.  That chord is spelled D – A – F# - Cnatural.  The interval between the 3rd and the 7th, in this case F# to Cnatural, is a tritone.  It is the tritone that gives the 7th chord its power. 

You’ll find the tritone in diminished chords, too.  After all, there is no difference in how an augmented 4th and diminished 5th are heard.  The tones are “enharmonic”. They sound identical.  A diminished chord is spelled:  1 – 3minor – 5diminished.  The tritone lies between the root 1 and the diminished 5th.

In tonal music the tension created by the existence of the tritone is usually resolved by movement downward to the interval of a third above the root of the chord supporting the phrase. 

A perfect example of this movement is John Lennon’s song Imagine.

The melody line in the second measure that begins on the first syllable of “heaven”, creates a tritone.  The C# played against the G chord produces the tritone and great tension.  Playing by expectations of harmonic movement, the melody line resolves downward to a 3rd above the root tone of G. 

Another clear example of the use of the tritone occurs in Leonard Berstein’s song Maria from the musical West Side Story.  But in this case the melody line moves upward to resolve to a 5th above the tonic:   Ma (root) – ri(tritone) – a (5th above the root).

Broadway musicals not your thing?  Okay, try a cartoon show.  The very same upward resolution of the tritone that appears in Berstein's Maria is found in the opening sequence of the TV Cartoon show The Simpsons.  The (root)  Simp (tritone)  sons (5th above the root)

Anytime a composer introduces a note that is three whole tones distant from the key of a piece or of the current chord in the piece, the listener’s sense of tonality is injured, if not destroyed.  This technique is an essential tool used to create tension in music. 

Whenever you feel great tension in music that is quickly resolved to tranquility, expect to find the tritone. After all, it is the devil in music!

Want to go deeper into the subject?  Look at this Wikipedia post that discusses the “tritone paradox”.  Also explore the links for “Shepard Tone”.

http://en.wikipedia.org/wiki/Tritone_paradox

Listen to the Shepard tone here:
http://en.wikipedia.org/wiki/Shepard_tone
http://www.youtube.com/watch?v=DfJa3IC1txI