Implement new rules

[Dylan-Riley]

Read the second species of counterpoint, take notes, compare with Haoran's: chap2_rulesDraft.pdf

I need to know for myself just how much the old rules continue to track. Only really StartEndPerfect and maybe Battuta make sense in the new format, but battuta also seems to have been modified going over Haoran's notes.

[Dylan-Riley]

Other updates to add based on today meeting: Add the thing to the new recursive call to keep track of the counterpoint solution thus far.

[Dylan-Riley]

The Second Species of Counterpoint:

• Downbeats* must always be consonant
• Dissonance is allowed on upbeats if stepwise between the two downbeats
• If a series of notes would be a skip they must all be consonant
• Penultimate measure:
  • If the cantus firmus is the lower voice this measure's counterpoint should include a movement of a fifth followed by a sixth
  • If the cantus firmus is the upper, counterpoint fifth then minor third
  • (These are going to be hard to implement)
• Two downbeat fifths cannot be interupted by a third. Fourths and sixths are okay, or don't have two fifths in a row
• If the parts come too close together (in the example CP stays static while the CF moves from close underneath to close above) CP can and should jump away by a sixth or an octave
• Mi against Fa still applies
  • Do not match the mi from one hexachord with the fa from another hexachord
  • Can probably be cheated by just not allowing a B natural against an F
• If there are multiple notes over a single note (example three over one) the middle not can be dissonant if stepwise

* A downbeat can include what is actually a downbeat, or the middle note of three same lengths. Fux uses this to mean halfs in second species, and then quarters in the third species

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Some of these involve dissonance. That might require a little change to the note cloud generation if we want to worry about that right now. Say to use rules to force consonance or dissonance in certain patterns, which -- now that I type that out -- that specifically sounds really complicated.

I've also skimmed third species a little and some of what it covers would be useful. Grab some of that tomorrow.

[Dylan-Riley]

Did a bit more research on the Mi against Fa bit and tritones, apparently this is a pretty old way of thinking even for Fux. It is mostly for the B natural over F tritone since both those notes appear in the hexachords, but because the tritone sounds spooky dissonant it was deemed the devil's interval and banned.

To comply with this either just remove the six semitones option from generation or write a rule specifically to disallow tritones from the hexachords.