Merge pull request #2044 from float3/derive-with-altered-degrees

Author: mscuthbert

music21/scale/__init__.py

@@ -2486,7 +2486,8 @@ def derive(self, other, comparisonAttribute: str = 'pitchClass') -> ConcreteScal
         abstract = t.cast(AbstractScale, self._abstract)
         net = t.cast('intervalNetwork.IntervalNetwork', abstract._net)
         pairs = net.find(pitchTarget=otherPitches,
-                         comparisonAttribute=comparisonAttribute)
+                         comparisonAttribute=comparisonAttribute,
+                         alteredDegrees=abstract._alteredDegrees)
 
         newScale = self.__class__(tonic=pairs[0][1])
         if newScale.abstract is None:

music21/scale/test_scale_main.py

@@ -286,6 +286,10 @@ def testHarmonicMinorDescendingRange(self):
         descending = sc.getPitches('c#4', 'g#4', direction=Direction.DESCENDING)
         self.assertEqual(self.pitchOut(descending), '[G-4, F4, E-4, D-4]')
 
+    def testDeriveHarmonicMinor(self):
+        sc = scale.HarmonicMinorScale()
+        self.assertEqual(sc.derive(['C', 'D', 'E-', 'B']).name, 'C harmonic minor')
+
     def testDeriveByDegree(self):
         sc1 = scale.MajorScale()
         self.assertEqual(str(sc1.deriveByDegree(7, 'G#')),