The four-semitone tritone scale (set 10-6) is a decatonic scale consisting of four semitones, a whole tone, four semitones, and a whole tone (four semitones a
tritone apart): 0,1,2,3,4,6,7,8,9,10. This may be related to the seven notes of the diatonic scale as, "1 ♭2 ♮2 ♭3 ♮3 ♯4 ♮5 ♭6 ♮6 ♭7," and thus spelled, on C, as C, D♭, D♮, E♭, E♮, F♯, G, A♭, A♮, B♭.[1] This is a mode of
Olivier Messiaen's seventh
mode of limited transposition; it has six transpositions, like the tritone, and five modes (the same pitch classes with C, D♭, D, E♭, or E taken as the first
scale step or tonic). This allows a
dominant seventh chord to be built upon the
tonic and a
seventh sharp nine chord, and allows the tonic chord to have an
alteredninth,
eleventh, and
thirteenthfactors.[1] However,
pitch sets containing more than seven notes become increasingly similar to each other.[4]
^Hanson, Howard. (1960) Harmonic Materials of Modern Music, p. 33. New York: Appleton-Century-Crofts. LOC 58-8138. "When the projection [of the perfect fifth] is carried beyond seven tones, no new intervals can be added." "On the other hand, as sonorities are projected beyond the six-tone series they tend to lose their individuality. All seven-tone series, for example, contain all of the six basic intervals, and difference in their proportion decreases as additional tones are added ... Such patterns tend to lose their identity, producing a monochromatic effect with its accompanying lack of the essential element of contrast."