Class: HeadMusic::Style::Guidelines::SuspensionTreatment

Inherits:
HeadMusic::Style::Guideline show all
Defined in:
lib/head_music/style/guidelines/suspension_treatment.rb

Overview

A counterpoint guideline for fourth species suspension treatment. A suspension has three parts: 1. Preparation: The note is consonant with the current cantus firmus note. 2. Suspension: The cantus firmus moves; the counterpoint sustains, becoming dissonant. 3. Resolution: The counterpoint resolves by step down to a consonance.

Instance Method Summary collapse

Constructor Details

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

Instance Method Details

#consonant_at?(position) ⇒ Boolean (private)

Returns:

  • (Boolean) 


64
65
66
67
 
# File 'lib/head_music/style/guidelines/suspension_treatment.rb', line 64

def consonant_at?(position)
  interval = harmonic_interval_at(position)
  two_part?(interval) && interval.consonance?(:two_part_harmony)
end

#dissonant_at?(position) ⇒ Boolean (private)

Returns:

  • (Boolean) 


59
60
61
62
 
# File 'lib/head_music/style/guidelines/suspension_treatment.rb', line 59

def dissonant_at?(position)
  interval = harmonic_interval_at(position)
  two_part?(interval) && interval.dissonance?(:two_part_harmony)
end

#dissonant_suspensions ⇒ Object (private) 



24
25
26
27
28
29
 
# File 'lib/head_music/style/guidelines/suspension_treatment.rb', line 24

def dissonant_suspensions
  cantus_firmus.notes[1..].filter_map do |cf_note|
    cp_note = suspended_cp_note(cf_note)
    [cp_note, cf_note] if cp_note && dissonant_at?(cf_note.position)
  end
end

#harmonic_interval_at(position) ⇒ Object (private) 



69
70
71
 
# File 'lib/head_music/style/guidelines/suspension_treatment.rb', line 69

def harmonic_interval_at(position)
  HeadMusic::Analysis::HarmonicInterval.new(cantus_firmus, voice, position)
end

#improperly_treated_suspensions ⇒ Object (private) 



20
21
22
 
# File 'lib/head_music/style/guidelines/suspension_treatment.rb', line 20

def improperly_treated_suspensions
  dissonant_suspensions.reject { |note, cf_note| properly_treated?(note, cf_note) }.map(&:first)
end

#marks ⇒ Object 



10
11
12
13
14
15
16
 
# File 'lib/head_music/style/guidelines/suspension_treatment.rb', line 10

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

  improperly_treated_suspensions.map do |note|
    HeadMusic::Style::Mark.for(note)
  end
end

#prepared?(cp_note, cf_note) ⇒ Boolean (private)

Returns:

  • (Boolean) 


42
43
44
45
46
47
 
# File 'lib/head_music/style/guidelines/suspension_treatment.rb', line 42

def prepared?(cp_note, cf_note)
  prev_cf = previous_cf_note(cf_note)
  return false unless prev_cf

  consonant_at?(cp_note.position)
end

#previous_cf_note(cf_note) ⇒ Object (private) 



77
78
79
80
 
# File 'lib/head_music/style/guidelines/suspension_treatment.rb', line 77

def previous_cf_note(cf_note)
  index = cantus_firmus.notes.index(cf_note)
  cantus_firmus.notes[index - 1] if index && index > 0
end

#properly_treated?(cp_note, cf_note) ⇒ Boolean (private)

Returns:

  • (Boolean) 


38
39
40
 
# File 'lib/head_music/style/guidelines/suspension_treatment.rb', line 38

def properly_treated?(cp_note, cf_note)
  prepared?(cp_note, cf_note) && resolved?(cp_note, cf_note)
end

#resolved?(cp_note, _cf_note) ⇒ Boolean (private)

Returns:

  • (Boolean) 


49
50
51
52
53
54
55
56
57
 
# File 'lib/head_music/style/guidelines/suspension_treatment.rb', line 49

def resolved?(cp_note, _cf_note)
  next_cp = voice.note_following(cp_note.position)
  return false unless next_cp

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

  consonant_at?(next_cp.position)
end

#suspended_cp_note(cf_note) ⇒ Object (private)

The counterpoint note sounding under the cantus firmus note, but only when it began earlier (a note held over, i.e. a suspension).



33
34
35
36
 
# File 'lib/head_music/style/guidelines/suspension_treatment.rb', line 33

def suspended_cp_note(cf_note)
  cp_note = voice.note_at(cf_note.position)
  cp_note if cp_note && cp_note.position < cf_note.position
end

#two_part?(interval) ⇒ Boolean (private)

Returns:

  • (Boolean) 


73
74
75
 
# File 'lib/head_music/style/guidelines/suspension_treatment.rb', line 73

def two_part?(interval)
  interval.notes.length == 2
end