Editing Tritone (section)

=== Strict interpretation (diatonic scale) ===
Within a [[diatonic scale]], whole tones are always formed by adjacent notes (such as C and D) and therefore they are regarded as [[incomposite interval]]s. In other words, they cannot be divided into smaller intervals. Consequently, in this context the above-mentioned "decomposition" of the tritone into six semitones is typically not allowed.

If a diatonic scale is used, with its 7 notes it is possible to form only one sequence of three adjacent whole tones (''T+T+T''). This interval is an A4. For instance, in the [[C major]] diatonic scale (C–D–E–F–G–A–B–...), the only tritone is from F to B. It is a tritone because F–G, G–A, and A–B are three adjacent whole tones. It is a ''fourth'' because the notes from F to B are four (F, G, A, B). It is ''augmented'' (i.e., widened) because it is wider than most of the fourths found in the scale (they are [[perfect fourth]]s).

According to this interpretation, the d5 is not a tritone. Indeed, in a diatonic scale, there is only one d5, and this interval does not meet the strict definition of tritone, as it is formed by one semitone, two whole tones, and another semitone:

: ''d5 = S+T+T+S''.

For instance, in the C major diatonic scale, the only d5 is from B to F. It is a ''fifth'' because the notes from B to F are five (B, C, D, E, F). It is ''diminished'' (i.e. narrowed) because it is smaller than most of the fifths found in the scale (they are [[perfect fifth]]s).