Figure 8. The four species of 5th in each genus. Each species retains a similar abstract structure (e.g. abaaabaaa) to the diatonic when mapped to the other two genera, but the step intervals a and b are transformed from tones and semitones into the characteristic intervals of the other genera. Between angle brackets the number of scale steps (31sts of an 8ve) of each interval is given, always summing to 18 (a perfect 5th). The species of 5th are shown here at their traditional pitch heights.