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These options can be selected in the "Independence" section of the Choose Style window when in Free Counterpoint.
Definitions: Two voices have similar motion if they both either ascend or descend. Similar motion is parallel if both voices move by the same interval. They have contrary motion if one ascends as the other descends, and their motion is oblique if one remains at the same pitch while the other changes pitch.
Avoid parallel fifths and octaves between adjacent notes. If two notes are separated by a perfect fifth or octave and move in the same direction by the same amount, they are creating parallel perfect intervals. These have traditionally been considered to diminish the sense of independence of voices. Example:
Allow if syncopated.
Allow 5ths if contrary and at least one voice is inner.
Allow if at least one of the notes is "unessential." An "unessential" pitch is one that is not part of the prevailing harmony. It may or may not be dissonant. This applies more in tonal (18th century) than in modal counterpoint.
Avoid parallel fifths and octaves between any part of a beat and an accented note on the next beat. This is a strict standard. An example:
Allow if the first notes don't begin simultaneously The syncopated effect would tend to hide the parallel.
Allow if both first notes are offbeat.
Allow if intervening notes are concords. An intervening concord has traditionally been thought to "save" a parallel.
Avoid parallel fifths and octaves between notes on adjacent accents, if voices are 2:1 (second species).
Allow if the faster voice leaps by more than a third from the first perfect interval. Fux (Mann, p. 43 f.) holds that such a leap distracts the ear from the parallel.
Allow if intervening note is concordant. In Fux's second species a leap to a dissonance is not permitted, so this in effect relaxes the above Fux rule to include even concords reached stepwise.
Avoid parallel fifths and octaves between notes following adjacent accents, if voices are 2:1 (second species).
Allow if each of the notes forming the parallel is approached from a different direction.
Allow if each of the perfect intervals is "unessential" (not part of the prevailing harmony).
Avoid "direct"or "hidden" 5ths or 8vas (similar motion to those intervals). Sometimes also called "covered" fifths or octaves, these are harder to notice than parallels.
Allow if disguised through syncopation.
Allow at cadence in 3+ voices.
Allow if one voice is inner and exposed voice moves by step. Bach does this fairly often in his Chorales.
Direct 5th allowed in outer parts if upper voice moves by step. (But not the direct octave - just fifths can use this exception).
Direct 5th or 8va allowed in outer parts if 4 or more voices and upper is by step.
Avoid leaping motion in two voices moving to a perfect interval. This includes even contrary motion if both voices move by leap.
Allow if either is an inner part.
Avoid similar motion in more than two voices at once (impossible in more than 4 parts). If there are more than four parts then of course three of them must be moving in similar or oblique motion.
Avoid similar motion in outer voices. This would be an impossible standard in two-part writing, but could be accomplished in three or four parts.
Avoid similar motion from a 2nd to a 3rd. The smoothest resolution of the dissonance of a second comes when the lower tone moves downward a step. This rule would stop you from writing an awkward resolution involving an overlap, as follows:
Avoid parallel fourths. The fourth is has a double nature: it is the inversion of the consonant perfect fifth, but acoustically its root is its upper note and due to instability it is regarded as a discord when its lower tone is the bass. The perfect nature of the interval raises the same objections as the fifth and octave if this interval is written parallel. But when combined with the pitch class a third below its lower tone it forms the familiar 1st inversion of a triad, and will then often be seen written in a parallel sequence.
Allow if combined with a third below the lower tone:
Allow if syncopated
Allow if at least one of the notes is "unessential."
Avoid parallel major thirds (owing to tritone effect). Two successive major thirds will produce a tritone between the first note of the lower voice and the second note of the upper voice. Yet this is sometimes found even in Palestrina:
Allow if no more than two in succession.
Avoid overlapping voices. Voices are said to overlap when the lower one moves to a pitch at or above the previous pitch of the higher voice. An example would be the similar motion of a 2nd to a 3rd, as illustrated above.
Avoid crossing voices. Crossing is more than an overlap; the lower voice becomes the higher, and vice-versa. Crossing is sometimes forbidden just as an exercise, but Jeppeson (p. 113) remarks that without crossing "no real polyphony is possible."
Allow crossing in upper voices if more than two parts.This would be a sensible exception if you want to try limiting crossing.
Avoid more than 3 successive uses of the same interval in the same voices (allowed in 3+ parts or when crossing). One may be tempted to let two voices move in thirds or sixths continually, but if this continues for long the independence of voices is lost.
Avoid following a perfect consonance with another one. Two voices forming a perfect fifth should not immediately proceed to an octave, or vice-versa.
Avoid unisons. This would be most significant in two-part writing, though it may be desirable to try avoiding unisons even in three and four parts.
OK in an initial or a final sonority.
OK for interior measures if not the first note of measure. The first note of a measure would carry the most emphasis.
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