
1) Augmented fourth 2) Musical interval 3) Three-note musical interval 4) Three-step musical interval
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https://www.crosswordclues.com/clue/tritone

In music theory, the tritone is strictly defined as a musical interval composed of three adjacent whole tones. For instance, the interval from F up to the B above it (in short, F–B) is a tritone as it can be decomposed into the three adjacent whole tones F–G, G–A, and A–B. According to this definition, within a diatonic scale there is only...
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http://en.wikipedia.org/wiki/Tritone

• (n.) A superfluous or augmented fourth.
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http://thinkexist.com/dictionary/meaning/tritone/

in music, the interval encompassed by three consecutive whole steps, as for instance the distance from F to B (the whole steps F–G, G–A, and A–B). In ... [2 related articles]
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http://www.britannica.com/eb/a-z/t/82

this is an interval using three whole-tones (tri-tone). It is normally an augmented fourth, or a diminished fifth
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http://www.encyclo.co.uk/local/20596

A black and white image printed with three screens and three colours, such as one black and two greys, used to enrich the contrast between light and dark areas.
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http://www.encyclo.co.uk/local/20829

In music a tritone is a superfluous or augmented fourth.
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http://www.probertencyclopaedia.com/browse/VT.HTM

tritone An interval composed of three whole tones. The tritone derives its name from the fact that it spans three whole tones and it refers to any musical interval of six semitones. Two tritones add up to six whole tones or twelve semitones which are usually a perfect octave. An augmented fourth or diminished or flatted fifth is a tritone.
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http://www.wordinfo.info/words/index/info/view_unit/2185/

The interval of three whole steps, i.e. an augmented 4th or diminished 5th.
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https://www.apassion4jazz.net/glossary5.html

A chord comprised of three whole tones resulting in an augmented fourth or diminished fifth.
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https://www.encyclo.co.uk/local/21781
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