E) generates a major third consisting of two whole tones A chain of three fourths generates a minor third (A, D, G, C) and so on; in all those examples the result is reduced to the octave. If one continues to increase the size of the S further, so that it is larger than the T, one gets scales with two large steps and five small steps, and eventually, when all the T's vanish the result is SS, so a tritone division of the octave. These scales however are not included as regular diatonic tunings. All regular diatonic tunings are also linear temperaments, i.e. Regular temperaments with two generators: the octave and the tempered fifth. One can use the tempered fourth as an alternative generator (e.g. as B E A D G C F, ascending fourths, reduced to the octave), but the tempered fifth is the more usual choice. All regular diatonic tunings are also Generated collections (also called Moments of Symmetry) and the chain of fifths can be continued in either direction to obtain a twelve tone system F C G D A E B F# C# G# D# A# where the interval F#-G is the same as B - C etc., another moment of symmetry with two interval sizes. A chain of seven fifths generates a chromatic semitone, for instance from F to F# and the pattern of chromatic and diatonic semitones is CDCDDCDCDCDD or a permutation of it where the C is the chromatic semitone, and D is the diatonic semitone e.g. from E to F between notes five steps apart in the cycle. Here, the seven equal system is the limit as the chromatic semitone tends to zero, and the five tone system in the limit as the diatonic semitone tends to zero. Range of recognizability The regular diatonic tunings include all linear temperaments within Easley Blackwood's "Range of Recognizability" in his The Structure of Recognizable Diatonic Tunings for diatonic tunings with the fifth tempered to between 4/7 and 3/5 of an octave; the major and minor seconds both positive; the major second larger than the minor second. However, his "range of recognizability" is more restrictive than "regular diatonic tuning". For instance, he requires the diatonic semitone to be at least 25 cents in size. See for a summary. Significant regions within the range When the fifths are a little flatter than the 700 cents of