The Avoidance of Part-Crossing in Polyphonic Music:

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The Avoidance of Part-Crossing in Polyphonic
Music Perceptual Evidence and Musical Practice
David Huron
Presented by Zhenyao Mo
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Dowlings Observation
Two Concurrent interleaved melodies
Transpose
Without pitch overlay
Part Crossing
Easy to segregate
Hard to segregate
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Three Hypothesis
Pitch Domain
Time Domain
Tessitura
Range Overlap
Local Crossing
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Two Questions

• Is the avoidance of part-crossing on purpose or
  just because the different pitch distributions
  for various voices?
• Is the purpose of such avoidance to prevent the
  sort of perceptual confusions, say, can not
  segregate different parts?

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Subjects 105 polyphonic keyboard works by Bach
Why???

• As for choral works, different parts have their
  own instrumental or vocal range, while keyboard
  music parts are relatively free to traverse whole
  range
• In keyboard music the parts maintain homogeneous
  timbers

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Measurement of Part-Crossing

• Sonority each novel vertical pitch arrangement
  between two voices can be deemed a distinct
  sonority
• Degree of part-crossing proportion of vertical
  sonorities in which a part crossing has occurred

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Some Facts
Number of Parts Two Three Four Five Six
Degree of part-crossing Mean () 0.18 0.79 1.78 3.11 6.11
Standard Deviation of Pitch 5.65 4.71 4.47 4.33 3.94
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Auto-Phase Method
Aim To distinguish Local crossing from
tessitura and range overlap
Basic idea keep the pitch range, but regenerate
the order or correspondence
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More Facts
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More Facts
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Two Questions

• Is the avoidance of part-crossing on purpose or
  just because the different pitch distributions
  for various voices?
• NO
• Is the purpose of such avoidance to prevent the
  sort of perceptual confusions, say, can not
  segregate different parts?
• YES, we got evidence.

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Thank You