Class: HeadMusic::Analysis::Dyad

Inherits:
Object
  • Object
show all
Defined in:
lib/head_music/analysis/dyad.rb,
lib/head_music/analysis/dyad/chord_implication.rb

Overview

A Dyad is a two-pitch combination that can imply various chords. It analyzes the harmonic implications of two pitches sounding together.

Defined Under Namespace

Classes: ChordImplication

Constant Summary collapse

ALTERATION_SIGNS = 
{-2 => "bb", -1 => "b", 0 => "", 1 => "#", 2 => "##"}.freeze

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(pitch1, pitch2, key: nil) ⇒ Dyad

Returns a new instance of Dyad.



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# File 'lib/head_music/analysis/dyad.rb', line 9

def initialize(pitch1, pitch2, key: nil)
  @pitch1, @pitch2 = [
    HeadMusic::Rudiment::Pitch.get(pitch1),
    HeadMusic::Rudiment::Pitch.get(pitch2)
  ].sort
  @key = key ? HeadMusic::Rudiment::Key.get(key) : nil
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(method_name, *args, &block) ⇒ Object 



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# File 'lib/head_music/analysis/dyad.rb', line 53

def method_missing(method_name, *args, &block)
  respond_to_missing?(method_name) ? interval.send(method_name, *args, &block) : super
end

Instance Attribute Details

#key ⇒ Object (readonly)

Returns the value of attribute key.



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# File 'lib/head_music/analysis/dyad.rb', line 7

def key
  @key
end

#pitch1 ⇒ Object (readonly)

Returns the value of attribute pitch1.



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# File 'lib/head_music/analysis/dyad.rb', line 7

def pitch1
  @pitch1
end

#pitch2 ⇒ Object (readonly)

Returns the value of attribute pitch2.



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# File 'lib/head_music/analysis/dyad.rb', line 7

def pitch2
  @pitch2
end

Instance Method Details

#all_spellings ⇒ Object (private) 



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# File 'lib/head_music/analysis/dyad.rb', line 93

def all_spellings
  HeadMusic::Rudiment::LetterName.all.flat_map do |letter_name|
    ALTERATION_SIGNS.each_value.map { |sign| HeadMusic::Rudiment::Spelling.get("#{letter_name}#{sign}") }
  end.compact
end

#chord_implication ⇒ Object (private) 



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# File 'lib/head_music/analysis/dyad.rb', line 63

def chord_implication
  @chord_implication ||= ChordImplication.new([lower_pitch.pitch_class, upper_pitch.pitch_class], key)
end

#enharmonic_equivalents_for(pitch) ⇒ Object (private) 



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# File 'lib/head_music/analysis/dyad.rb', line 82

def enharmonic_equivalents_for(pitch)
  equivalent_pitches = enharmonic_spellings_for(pitch.pitch_class).map do |spelling|
    HeadMusic::Rudiment::Pitch.fetch_or_create(spelling, pitch.register)
  end
  [pitch, *equivalent_pitches].uniq(&:spelling)
end

#enharmonic_respellings ⇒ Object 



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# File 'lib/head_music/analysis/dyad.rb', line 45

def enharmonic_respellings
  @enharmonic_respellings ||= generate_enharmonic_respellings
end

#enharmonic_spellings_for(target_pitch_class) ⇒ Object (private) 



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# File 'lib/head_music/analysis/dyad.rb', line 89

def enharmonic_spellings_for(target_pitch_class)
  all_spellings.select { |spelling| spelling.pitch_class == target_pitch_class }
end

#generate_enharmonic_respellings ⇒ Object (private) 



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# File 'lib/head_music/analysis/dyad.rb', line 67

def generate_enharmonic_respellings
  lower_equivalents = enharmonic_equivalents_for(pitch1)
  upper_equivalents = enharmonic_equivalents_for(pitch2)

  lower_equivalents.product(upper_equivalents)
    .reject { |lower, upper| original_spelling?(lower, upper) }
    .map { |lower, upper| self.class.new(lower, upper, key: key) }
end

#interval ⇒ Object 



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# File 'lib/head_music/analysis/dyad.rb', line 17

def interval
  @interval ||= HeadMusic::Analysis::DiatonicInterval.new(lower_pitch, upper_pitch)
end

#lower_pitch ⇒ Object 



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# File 'lib/head_music/analysis/dyad.rb', line 25

def lower_pitch
  @lower_pitch ||= [pitch1, pitch2].min
end

#original_spelling?(lower, upper) ⇒ Boolean (private)

Returns:

  • (Boolean) 


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# File 'lib/head_music/analysis/dyad.rb', line 76

def original_spelling?(lower, upper)
  lower.spelling == pitch1.spelling && upper.spelling == pitch2.spelling
end

#pitches ⇒ Object 



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# File 'lib/head_music/analysis/dyad.rb', line 21

def pitches
  [pitch1, pitch2]
end

#possible_seventh_chords ⇒ Object 



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# File 'lib/head_music/analysis/dyad.rb', line 41

def possible_seventh_chords
  chord_implication.seventh_chords
end

#possible_triads ⇒ Object 



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# File 'lib/head_music/analysis/dyad.rb', line 37

def possible_triads
  @possible_triads ||= possible_trichords.select(&:triad?)
end

#possible_trichords ⇒ Object 



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# File 'lib/head_music/analysis/dyad.rb', line 33

def possible_trichords
  chord_implication.trichords
end

#respond_to_missing?(method_name, *_args) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/head_music/analysis/dyad.rb', line 57

def respond_to_missing?(method_name, *_args)
  interval.respond_to?(method_name)
end

#to_s ⇒ Object 



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# File 'lib/head_music/analysis/dyad.rb', line 49

def to_s
  "#{pitch1} - #{pitch2}"
end

#upper_pitch ⇒ Object 



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# File 'lib/head_music/analysis/dyad.rb', line 29

def upper_pitch
  @upper_pitch ||= [pitch1, pitch2].max
end