Whether two voices arrive at a perfect octave or unison by contrary motion with the upper voice leaping down — the ottava battuta the sixteenth-century theorists forbid.
The stepwise arrival is allowed, as is the same octave reached with the upper voice rising, so only the downward leap into the perfect class is flagged. Arriving at a perfect class the voices were already sitting on (e.g. octave to octave by contrary motion) is the anti-parallel case owned by createsParallelPerfect; battuta is reserved for a perfect class that was not already there.
Whether two voices arrive at a perfect octave or unison by contrary motion with the upper voice leaping down — the ottava battuta the sixteenth-century theorists forbid.
The stepwise arrival is allowed, as is the same octave reached with the upper voice rising, so only the downward leap into the perfect class is flagged. Arriving at a perfect class the voices were already sitting on (e.g. octave to octave by contrary motion) is the anti-parallel case owned by createsParallelPerfect; battuta is reserved for a perfect class that was not already there.