music21.figuredBass.rules

Rules

class music21.figuredBass.rules.Rules

A Rules object is provided as an input to a Segment, and controls the application of methods designed to filter out undesired possibilities in a single Segment or undesired progressions between two consecutive Segments.

The rules are categorized in an identical manner to methods in possibility:

1) Single Possibility Rules. These rules apply to any possibility within a single Segment (possibA), and are applied in finding correct possibilities for a Segment in allCorrectSinglePossibilities().

2) Consecutive Possibility Rules. These rules apply between any correct single possibility in segmentA (possibA) and any correct single possibility in segmentB (possibB), segmentB coming directly after segmentA. They are applied in finding correct (possibA, possibB) pairs between two Segments in allCorrectConsecutivePossibilities().

3) Special Resolution Rules. These rules apply to Segments whose segmentChord is an augmented sixth, dominant seventh, or diminished seventh chord, and are applied as necessary in allCorrectConsecutivePossibilities().

>>> from music21.figuredBass import rules
>>> fbRules = rules.Rules()
>>> fbRules
<music21.figuredBass.rules.Rules>
>>> fbRules.forbidParallelFifths = False
>>> fbRules.upperPartsMaxSemitoneSeparation = None

Rules bases

Rules read-only properties

Read-only properties inherited from ProtoM21Object:

Rules methods

Methods inherited from ProtoM21Object:

Rules instance variables

Rules.applyConsecutivePossibRulesToResolution

False by default. If True, consecutive possibility rules are applied between (specialPossib, resPossib) pairs.

Rules.applySinglePossibRulesToResolution

False by default. If True, single possibility rules are applied to resolution possibilities.

Rules.doubledRootInDim7

False by default. If True, Diminished seventh resolutions to the tonic will contain a doubled root, as opposed to a doubled third. Rule is ignored (determined in context) if segmentChord is in first inversion.

Rules.forbidHiddenFifths

True by default. If True, hiddenFifth() is applied to all (possibA, possibB) pairs, and all those pairs for which the method returns False are retained.

Rules.forbidHiddenOctaves

True by default. If True, hiddenOctave() is applied to all (possibA, possibB) pairs, and all those pairs for which the method returns False are retained.

Rules.forbidIncompletePossibilities

True by default. If True, isIncomplete() is applied to all possibA, and all those possibilities for which the method returns False are retained.

Rules.forbidParallelFifths

True by default. If True, parallelFifths() is applied to all (possibA, possibB) pairs, and all those pairs for which the method returns False are retained.

Rules.forbidParallelOctaves

True by default. If True, parallelOctaves() is applied to all (possibA, possibB) pairs, and all those pairs for which the method returns False are retained.

Rules.forbidVoiceCrossing

True by default. If True, voiceCrossing() is applied to all possibA, and all those possibilities for which the method returns False are retained.

Rules.forbidVoiceOverlap

True by default. If True, voiceOverlap() is applied to all (possibA, possibB) pairs, and all those pairs for which the method returns False are retained.

Rules.partMovementLimits

[] (empty list) by default. Contains (partNumber, maxSeparation) pairs provided as arguments to partMovementsWithinLimits(). Method is applied to all (possibA, possibB) pairs, and all those pairs for which the method returns True are retained.

Rules.resolveAugmentedSixthProperly

True by default. If True, Segments whose segmentChord spells out an augmented sixth chord are resolved properly by using resolveAugmentedSixthSegment().

Rules.resolveDiminishedSeventhProperly

True by default. If True, Segments whose segmentChord spells out a fully-diminished seventh chord are resolved properly by using resolveDiminishedSeventhSegment().

Rules.resolveDominantSeventhProperly

True by default. If True, Segments whose segmentChord spells out a dominant seventh chord are resolved properly by using resolveDominantSeventhSegment().

Rules.restrictDoublingsInItalianA6Resolution

True by default. If True, then doublings in the It+6 chord are limited to the tonic, or fifth. Setting this to False allows doubling of the root or third, most likely through parallel unisons if forbidParallelOctaves is set to True.

Rules.upperPartsMaxSemitoneSeparation

12 by default. A number, in semitones, representing the maxSemitoneSeparation argument provided to upperPartsWithinLimit(). Method is applied to all possibA, and all those possibilities for which the method returns True are retained.