I keep reading this set of rules for counterpoint.
The rule number G5 states:
If there are two horizontal intervals of equal distance and discordant, the next interval must differ.
I try to figure out in what situation the rule can be triggered. First, among the allowed intervals (m2, M2, m3, M3, P4, P5 and m6) only m2 and M2 are dissonant (discordant).
In a diatonic scale to m2 in a row are impossible. So, the only what remains is M2. Therefore, I guess, that the rule can be formulated like this:
If you go F - G - A, you are not allowed to go further to B. Similarly, if you go B - A - G, you are not allowed to go to F.
Is my interpretation correct?
There is a clarification of the rule, which made me even more confused:
Rule G5 is another case of IR. Many observations against redundancy, similar sequences and other forms of repetition can be found in all five textbooks we analysed. However, the supporting examples were extremely variable and context-dependant, and the prescriptions imprecise and subject to personal taste. Therefore, our rule vetoes only the most extreme form of repetition, the trill (see Figure 3)
Could it be that "discordant intervals", does not mean "dissonant" and, instead, it mean that intervals are in opposite direction?