Class: HeadMusic::Analysis::Circle

Inherits:
IntervalCycle show all
Defined in:
lib/head_music/analysis/circle.rb

Overview

A Circle of Fifths or Fourths shows relationships between pitch classes

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

This class inherits a constructor from HeadMusic::Analysis::IntervalCycle

Class Method Details

.get(interval = :perfect_fifth) ⇒ Object 



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# File 'lib/head_music/analysis/circle.rb', line 16

def self.get(interval = :perfect_fifth)
  @circles ||= {}
  diatonic_interval = HeadMusic::Analysis::DiatonicInterval.get(interval)
  @circles[interval] ||= new(interval: diatonic_interval, starting_pitch: "C4")
end

.of_fifths ⇒ Object 



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# File 'lib/head_music/analysis/circle.rb', line 8

def self.of_fifths
  get(:perfect_fifth)
end

.of_fourths ⇒ Object 



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# File 'lib/head_music/analysis/circle.rb', line 12

def self.of_fourths
  get(:perfect_fourth)
end

Instance Method Details

#index(pitch_class) ⇒ Object 



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# File 'lib/head_music/analysis/circle.rb', line 22

def index(pitch_class)
  pitch_classes.index(HeadMusic::Rudiment::Spelling.get(pitch_class).pitch_class)
end

#key_signatures_down ⇒ Object 



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# File 'lib/head_music/analysis/circle.rb', line 30

def key_signatures_down
  spellings_down.map { |spelling| HeadMusic::Rudiment::KeySignature.new(spelling) }
end

#key_signatures_up ⇒ Object 



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# File 'lib/head_music/analysis/circle.rb', line 26

def key_signatures_up
  spellings_up.map { |spelling| HeadMusic::Rudiment::KeySignature.new(spelling) }
end

#pitches_down ⇒ Object 



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# File 'lib/head_music/analysis/circle.rb', line 46

def pitches_down
  @pitches_down ||= [starting_pitch].tap do |list|
    loop do
      next_pitch = list.last - interval
      next_pitch += octave while starting_pitch - next_pitch > 12
      break if next_pitch.pitch_class == list.first.pitch_class

      list << next_pitch
    end
  end
end

#spellings_down ⇒ Object 



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# File 'lib/head_music/analysis/circle.rb', line 40

def spellings_down
  pitches_down.map(&:pitch_class).map do |pitch_class|
    pitch_class.smart_spelling(max_sharps_in_major_key_signature: 4)
  end
end

#spellings_up ⇒ Object 



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# File 'lib/head_music/analysis/circle.rb', line 34

def spellings_up
  pitches_up.map(&:pitch_class).map do |pitch_class|
    pitch_class.smart_spelling(max_sharps_in_major_key_signature: 7)
  end
end