The rule that was broken.
The voices involved, by index into a voicing (0 = lowest). A rule about a
pair names both, ascending; a rule about a single line names one. A
crossRelation is the exception: it names the voice holding the earlier
note first, whichever is higher. In a species exercise there are only two
voices and they are named by role instead: 0 is the cantus firmus and 1 the
counterpoint, whichever lies above.
Index of the chord the motion starts on; in a species exercise, the index into the counterpoint.
Index of the chord it ends on; equal to fromIndex for a vertical rule.
A short sentence naming the musical reason.
One broken rule, located in the progression and in the texture.