Class: HeadMusic::Style::Guidelines::FloridDissonanceTreatment

Inherits:
Annotation
  • Object
show all
Defined in:
lib/head_music/style/guidelines/florid_dissonance_treatment.rb

Overview

Unified dissonance handling for mixed-species (florid) contexts. - Strong beat dissonances must be properly prepared suspensions from a tie. - Weak beat dissonances must be passing tones or neighbor tones. - Tied notes dissonant at the new CF note must resolve by step to a consonance.

Constant Summary collapse

MESSAGE = 
"Treat dissonances appropriately: passing tones on weak beats, proper suspension treatment for tied notes."

Instance Method Summary collapse

Constructor Details

This class inherits a constructor from HeadMusic::Style::Annotation

Instance Method Details

#cantus_firmus_positions ⇒ Object (private) 



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# File 'lib/head_music/style/guidelines/florid_dissonance_treatment.rb', line 56

def cantus_firmus_positions
  @cantus_firmus_positions ||= Set.new(cantus_firmus.notes.map { |note| note.position.to_s })
end

#current_cf_note_at(position) ⇒ Object (private) 



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# File 'lib/head_music/style/guidelines/florid_dissonance_treatment.rb', line 60

def current_cf_note_at(position)
  cantus_firmus.note_at(position)
end

#dissonant_with_cantus?(note) ⇒ Boolean (private)

Returns:

  • (Boolean) 


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# File 'lib/head_music/style/guidelines/florid_dissonance_treatment.rb', line 64

def dissonant_with_cantus?(note)
  interval = HeadMusic::Analysis::HarmonicInterval.new(cantus_firmus, voice, note.position)
  interval.notes.length == 2 && interval.dissonance?(:two_part_harmony)
end

#following_note(note) ⇒ Object (private) 



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# File 'lib/head_music/style/guidelines/florid_dissonance_treatment.rb', line 92

def following_note(note)
  index = notes.index(note)
  notes[index + 1] if index && index < notes.length - 1
end

#improperly_treated_notes ⇒ Object (private) 



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# File 'lib/head_music/style/guidelines/florid_dissonance_treatment.rb', line 19

def improperly_treated_notes
  notes.select { |note| dissonant_with_cantus?(note) && !properly_treated?(note) }
end

#marks ⇒ Object 



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# File 'lib/head_music/style/guidelines/florid_dissonance_treatment.rb', line 11

def marks
  return [] unless cantus_firmus&.notes&.any?

  improperly_treated_notes.map { |note| HeadMusic::Style::Mark.for(note) }
end

#neighbor_tone?(note) ⇒ Boolean (private)

Returns:

  • (Boolean) 


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# File 'lib/head_music/style/guidelines/florid_dissonance_treatment.rb', line 73

def neighbor_tone?(note)
  stepwise_figure?(note, same_direction: false)
end

#on_strong_beat?(note) ⇒ Boolean (private)

Returns:

  • (Boolean) 


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# File 'lib/head_music/style/guidelines/florid_dissonance_treatment.rb', line 52

def on_strong_beat?(note)
  cantus_firmus_positions.include?(note.position.to_s)
end

#passing_tone?(note) ⇒ Boolean (private)

Returns:

  • (Boolean) 


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# File 'lib/head_music/style/guidelines/florid_dissonance_treatment.rb', line 69

def passing_tone?(note)
  stepwise_figure?(note, same_direction: true)
end

#preceding_note(note) ⇒ Object (private) 



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# File 'lib/head_music/style/guidelines/florid_dissonance_treatment.rb', line 87

def preceding_note(note)
  index = notes.index(note)
  notes[index - 1] if index && index > 0
end

#properly_treated?(note) ⇒ Boolean (private)

Returns:

  • (Boolean) 


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# File 'lib/head_music/style/guidelines/florid_dissonance_treatment.rb', line 23

def properly_treated?(note)
  if on_strong_beat?(note)
    properly_treated_suspension?(note)
  else
    passing_tone?(note) || neighbor_tone?(note)
  end
end

#properly_treated_suspension?(note) ⇒ Boolean (private)

A note on a strong beat that is dissonant must be a tied suspension (its position is before the CF note position, meaning it was held over).

Returns:

  • (Boolean) 


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# File 'lib/head_music/style/guidelines/florid_dissonance_treatment.rb', line 33

def properly_treated_suspension?(note)
  cf_note = current_cf_note_at(note.position)
  return false unless cf_note

  # The CP note must have started before the CF note (tied over)
  note.position < cf_note.position && resolved_by_step?(note)
end

#resolved_by_step?(note) ⇒ Boolean (private)

Returns:

  • (Boolean) 


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# File 'lib/head_music/style/guidelines/florid_dissonance_treatment.rb', line 41

def resolved_by_step?(note)
  next_cp = following_note(note)
  return false unless next_cp

  melodic = HeadMusic::Analysis::MelodicInterval.new(note, next_cp)
  return false unless melodic.step?

  # Resolution must be consonant
  !dissonant_with_cantus?(next_cp)
end

#stepwise_figure?(note, same_direction:) ⇒ Boolean (private)

Returns:

  • (Boolean) 


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# File 'lib/head_music/style/guidelines/florid_dissonance_treatment.rb', line 77

def stepwise_figure?(note, same_direction:)
  prev_note = preceding_note(note)
  next_note = following_note(note)
  return false unless prev_note && next_note

  approach = HeadMusic::Analysis::MelodicInterval.new(prev_note, note)
  departure = HeadMusic::Analysis::MelodicInterval.new(note, next_note)
  approach.step? && departure.step? && (approach.direction == departure.direction) == same_direction
end