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Mark an octave-repeating scale wider than an octave as not duplicating (AI) #2045

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Merged
mscuthbert merged 1 commit into from
Sep 23, 2026
Merged

Mark an octave-repeating scale wider than an octave as not duplicating (AI) #2045

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11 changes: 6 additions & 5 deletions music21/scale/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@
# Michael Scott Asato Cuthbert
# Jose Cabal-Ugaz
#
# Copyright: Copyright © 2009-2011 Michael Scott Asato Cuthbert
# Copyright: Copyright © 2009-2026 Michael Scott Asato Cuthbert
# License: BSD, see license.txt
# ------------------------------------------------------------------------------
'''
Expand Down Expand Up @@ -1005,10 +1005,6 @@ def __init__(self, mode: t.Any = None, **keywords) -> None:
mode = ['P8']
self.buildNetwork(mode=mode)

# by definition, these are forced to be octave duplicating
# though, do to some intervals, duplication may not happen every oct
self.octaveDuplicating = True

def buildNetwork(self, mode: t.Any = None) -> None:
'''
Here, mode is the list of intervals.
Expand All @@ -1022,6 +1018,11 @@ def buildNetwork(self, mode: t.Any = None) -> None:
if iComplement is not None:
mode.append(iComplement)

# steps wider than an octave complete a pattern spanning several
# octaves, which does not repeat every octave
span = intervalSum.semitones + (iComplement.semitones if iComplement else 0)
self.octaveDuplicating = span == 12
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self.tonicDegree = 1
self._net = intervalNetwork.IntervalNetwork(mode,
octaveDuplicating=self.octaveDuplicating)
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7 changes: 6 additions & 1 deletion music21/scale/test_scale_main.py
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Expand Up @@ -5,7 +5,7 @@
# Authors: Christopher Ariza
# Michael Scott Asato Cuthbert
#
# Copyright: Copyright © 2010-2024 Michael Scott Asato Cuthbert
# Copyright: Copyright © 2010-2026 Michael Scott Asato Cuthbert
# License: BSD, see license.txt
# ------------------------------------------------------------------------------
from __future__ import annotations
Expand Down Expand Up @@ -233,6 +233,11 @@ def testBasic(self):
<music21.pitch.Pitch F#5>],
'notMatched': [<music21.pitch.Pitch C#5>, <music21.pitch.Pitch G#5>]}''', pformat(sc1.match(sc2)))

def testOctaveRepeatingScaleWiderThanAnOctave(self):
sc = scale.OctaveRepeatingScale('c4', ['P5', 'P5'])
self.assertEqual(self.pitchOut(sc.pitches), '[C4, G4, D5, C6]')
self.assertEqual(self.pitchOut(sc.getPitches('c3', 'c6')), '[D3, C4, G4, D5, C6]')

def testCyclicalScales(self):
sc = scale.CyclicalScale('c4', ['m2', 'm2'])

Expand Down
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