Class: HeadMusic::Meter

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

Overview

Meter is the rhythmic size of a measure, such as 4/4 or 6/8

Constant Summary collapse

NAMED = 
{
  common_time: "4/4",
  cut_time: "2/2"
}.freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(top_number, bottom_number) ⇒ Meter

Returns a new instance of Meter.



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# File 'lib/head_music/meter.rb', line 32

def initialize(top_number, bottom_number)
  @top_number = top_number
  @bottom_number = bottom_number
end

Instance Attribute Details

#bottom_number ⇒ Object (readonly)

Returns the value of attribute bottom_number.



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# File 'lib/head_music/meter.rb', line 5

def bottom_number
  @bottom_number
end

#top_number ⇒ Object (readonly)

Returns the value of attribute top_number.



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# File 'lib/head_music/meter.rb', line 5

def top_number
  @top_number
end

Class Method Details

.common_time ⇒ Object 



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# File 'lib/head_music/meter.rb', line 24

def self.common_time
  get(:common_time)
end

.cut_time ⇒ Object 



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# File 'lib/head_music/meter.rb', line 28

def self.cut_time
  get(:cut_time)
end

.default ⇒ Object 



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# File 'lib/head_music/meter.rb', line 20

def self.default
  get("4/4")
end

.get(identifier) ⇒ Object 



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# File 'lib/head_music/meter.rb', line 12

def self.get(identifier)
  identifier = identifier.to_s
  hash_key = HeadMusic::Utilities::HashKey.for(identifier)
  time_signature_string = NAMED[hash_key] || identifier
  @meters ||= {}
  @meters[hash_key] ||= new(*time_signature_string.split("/").map(&:to_i))
end

Instance Method Details

#==(other) ⇒ Object 



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# File 'lib/head_music/meter.rb', line 95

def ==(other)
  to_s == other.to_s
end

#beat_strength(count, tick: 0) ⇒ Object 



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# File 'lib/head_music/meter.rb', line 65

def beat_strength(count, tick: 0)
  return 100 if downbeat?(count, tick)
  return 80 if strong_beat?(count, tick)
  return 60 if beat?(tick)
  return 40 if strong_ticks.include?(tick)

  20
end

#beat_unit ⇒ Object 



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# File 'lib/head_music/meter.rb', line 82

def beat_unit
  @beat_unit ||=
    if compound?
      HeadMusic::RhythmicValue.new(HeadMusic::RhythmicUnit.for_denominator_value(bottom_number / 2), dots: 1)
    else
      HeadMusic::RhythmicValue.new(count_unit)
    end
end

#beats_per_bar ⇒ Object 



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# File 'lib/head_music/meter.rb', line 57

def beats_per_bar
  compound? ? top_number / 3 : top_number
end

#compound? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/head_music/meter.rb', line 41

def compound?
  top_number > 3 && (top_number % 3).zero?
end

#count_unit ⇒ Object 



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# File 'lib/head_music/meter.rb', line 78

def count_unit
  HeadMusic::RhythmicUnit.for_denominator_value(bottom_number)
end

#counts_per_bar ⇒ Object 



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# File 'lib/head_music/meter.rb', line 61

def counts_per_bar
  top_number
end

#duple? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/head_music/meter.rb', line 45

def duple?
  top_number == 2
end

#quadruple? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/head_music/meter.rb', line 53

def quadruple?
  top_number == 4
end

#simple? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/head_music/meter.rb', line 37

def simple?
  !compound?
end

#strong_counts ⇒ Object 



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# File 'lib/head_music/meter.rb', line 99

def strong_counts
  @strong_counts ||= (1..counts_per_bar).select do |count|
    downbeat?(count) || strong_beat_in_duple?(count) || strong_beat_in_triple?(count)
  end
end

#strong_ticks ⇒ Object 



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# File 'lib/head_music/meter.rb', line 105

def strong_ticks
  @strong_ticks ||= [2, 3, 4].map { |sixths| ticks_per_count * (sixths / 6.0) }
end

#ticks_per_count ⇒ Object 



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# File 'lib/head_music/meter.rb', line 74

def ticks_per_count
  @ticks_per_count ||= count_unit.ticks
end

#to_s ⇒ Object 



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# File 'lib/head_music/meter.rb', line 91

def to_s
  [top_number, bottom_number].join("/")
end

#triple? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/head_music/meter.rb', line 49

def triple?
  (top_number % 3).zero?
end