Class: TransposeChords::Chord

Inherits:
Object
  • Object
show all
Defined in:
lib/transpose_chords.rb

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(keys) ⇒ Chord

Returns a new instance of Chord.



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# File 'lib/transpose_chords.rb', line 7

def initialize(keys)
  @keys = keys
end

Class Method Details

.transpose(keys) ⇒ Object 



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# File 'lib/transpose_chords.rb', line 3

def self.transpose(keys)
  new(keys)
end

Instance Method Details

#capo(fret) ⇒ Object 



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# File 'lib/transpose_chords.rb', line 39

def capo(fret)
  @keys.map do |k|
    key = table_key_for(k)
    table[:to_capo][key][fret]
  end
end

#key_indexes ⇒ Object 



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# File 'lib/transpose_chords.rb', line 50

def key_indexes
  @keys.map { |k|  keys_for(table_key_for(@keys.first))[k] }
end

#keys_for(key) ⇒ Object 



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# File 'lib/transpose_chords.rb', line 54

def keys_for(key)
  Hash[table[:to_key][key].map.with_index{|*ki| ki}]
end

#table ⇒ Object 



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# File 'lib/transpose_chords.rb', line 11

def table
  {
    to_key: {
      c: ['C', 'Dm', 'Em', 'F', 'G', 'Am', 'Bdim'],
      d: ['D', 'Em', 'F#m', 'G', 'A', 'Bm', 'C#dim'],
      e: ['E', 'F#m', 'G#m', 'A', 'B', 'C#m', 'D#dim'],
      f: ['F', 'Gm', 'Am', 'Bb', 'C', 'Dm', 'Edim'],
      g: ['G', 'Am', 'Bm', 'C', 'D', 'Em', 'F#dim'],
      a: ['A', 'Bm', 'C#m', 'D', 'E', 'F#m', 'G#dim'],
      b: ['B', 'C#m', 'D#m', 'E', 'F#', 'G#m', 'A#dim']
    },
    to_capo: {
      c: ['C', 'C#/Db', 'D', 'D#/Eb', 'E', 'F', 'F#/Gb', 'G'],
      d: ['D', 'D#/Eb', 'E', 'F', 'F#/Gb', 'G', 'Gb/Ab', 'A'],
      e: ['E', 'F', 'F#/Gb', 'G', 'G#/Ab', 'A', 'A#/Bb', 'B'],
      f: ['F', 'F#/Gb', 'G', 'G#/Ab', 'A', 'A#/Bb', 'B', 'C'],
      g: ['G', 'G#/Ab', 'A', 'A#/Bb', 'B', 'C', 'C#/Db', 'D'],
      a: ['A', 'A#/Bb', 'B', 'C', 'C#/Db', 'D', 'D#/Eb', 'E'],
      b: ['B', 'C', 'C#/Db', 'D', 'D#/Eb', 'E', 'F', 'F#/Gb']
    }
  }
end

#table_key_for(key) ⇒ Object 



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# File 'lib/transpose_chords.rb', line 46

def table_key_for(key)
  key.downcase.to_sym
end

#to(key) ⇒ Object 



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# File 'lib/transpose_chords.rb', line 34

def to(key)
  key = table_key_for(key)
  key_indexes.map { |k| table[:to_key][key][k] }
end