Tritone

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This article is about the musical interval. For other uses of the words, see tritone (disambiguation).

Template:Infobox Interval Image:Tritone.png The tritone, as its name implies, is a musical interval that spans three whole tones or six semitones. The two most basic types of tritone are the augmented fourth and the diminished fifth. Two tritones add up to 6 whole tones - or 12 semitones - usually a perfect octave. A common symbol for tritone is TT. A tritone may be heard here.

One of the two strong dissonances in the diatonic scale, it was called diabolus in musica ("the Devil's interval") by some from the early music era to the baroque period. It was exploited heavily in the Romantic period as an interval of modulation for its ability to evoke a strong reaction by entering the key least related (retaining only two common tones, the least possible) to what occurs previous.

The equal-tempered tritone (a ratio of <math>1 : \sqrt{2}</math> or 600 cents) is unique in being its own octave inversion. Note that in other temperaments such as meantone, the augmented fourth and the diminished fifth are distinct intervals because neither is exactly half an octave.

The tritone occurs naturally between the 4th and 7th scale degrees of the major scale (for example, in C major F to B), and depending on which of the two notes occurs in the bass, it is either an augmented 4th, or a diminished 5th. Its most common occurrence is between these scale degrees, in either inversion, when played as the third and seventh of the dominant seventh chord. The sound of the tritone in this chord is arguably what gives it its strong tendency towards resolution.

  • In jazz harmony, the tritone is both part of the dominant chord and its substitute dominant (also known as the sub V chord). Because they share the same tritone, they are possible substitutes for one another. This is known as tritone substitution.
    For example, in the key of C Major, the primary dominant G7 may be substituted with D♭7 which is its substitute dominant. Note that both have the same tritone (B and F, or enharmonically C♭ and F in reference to the D♭7 chord). In classical music Liszt uses the tritone in the same way in "Au bord d´une source" (B as dominant for B-flat) and many other places.
    This device can also be used in jazz improvisation, whereupon an improviser may use the chord tones of the D♭7 on a G7 chord to create an altered chord characteristic of jazz improvisation.
    The D♭7 chord tones spell out the ♭5, ♭7, ♭9 and maj3rd of the G7 chord, thus effectively outlining both the guide tones (maj3rd and ♭7) of the G7 as well as two altered notes (♭5 and ♭9).
  • Leonard Bernstein underpins almost all the music in West Side Story with persistent tritones. They feature as the opening interval to some of the songs, either melodically ("Maria" and "Cool" both begin with augmented fourths) or harmonically, when a flattened fifth is sung against a major chord ("Gee Officer Krupke"). Elsewhere, tritones figure prominently within "Something's Coming" and the "Jet Song", and the last sonority in the score is that of a high major chord with its own flattened fifth in the bass.
  • Danny Elfman uses tritones in his themes for The Simpsons (the first two notes of the opening choral "The Sim-" and the first and third notes of the main instrumental theme, for example) and Dilbert.

Template:Diatonic intervals

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External links

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