pitch.rb in music-transcription-0.16.0

- old
+ new

@@ -1,92 +1,108 @@
 module Music
 module Transcription
 
 # Abstraction of a musical pitch. Contains values for octave and semitone.
 #
-# Octaves represent the largest means of differing two pitches. Each 
-# octave added will double the ratio. At zero octaves, the ratio is 
+# Octaves represent the largest means of differing two pitches. Each
+# octave added will double the ratio. At zero octaves, the ratio is
 # 1.0. At one octave, the ratio will be 2.0. Each semitone is an increment
 # of less-than-power-of-two.
 #
 # Semitones are the primary steps between octaves. The number of
 # semitones per octave is 12.
 
 # @author James Tunnell
-# 
+#
 # @!attribute [r] octave
 #   @return [Fixnum] The pitch octave.
 # @!attribute [r] semitone
 #   @return [Fixnum] The pitch semitone.
 #
 class Pitch
   include Comparable
-  attr_reader :octave, :semitone, :total_semitone
+  attr_reader :octave, :semitone, :cent, :total_cents
 
-  #The default number of semitones per octave is 12, corresponding to 
+  #The default number of semitones per octave is 12, corresponding to
   # the twelve-tone equal temperment tuning system.
   SEMITONES_PER_OCTAVE = 12
+  CENTS_PER_SEMITONE = 100
+  CENTS_PER_OCTAVE = SEMITONES_PER_OCTAVE * CENTS_PER_SEMITONE
 
   # The base ferquency is C0
   BASE_FREQ = 16.351597831287414
-  
-  def initialize octave:0, semitone:0
+
+  def initialize octave:0, semitone:0, cent: 0
+    raise NonIntegerError, "octave #{octave} is not an integer" unless octave.is_a?(Integer)
+    raise NonIntegerError, "semitone #{semitone} is not an integer" unless semitone.is_a?(Integer)
+    raise NonIntegerError, "cent #{cent} is not an integer" unless cent.is_a?(Integer)
+    
     @octave = octave
     @semitone = semitone
+    @cent = cent
+    @total_cents = (@octave*SEMITONES_PER_OCTAVE + @semitone)*CENTS_PER_SEMITONE + @cent
     normalize!
-    @total_semitone = @octave*SEMITONES_PER_OCTAVE + @semitone
   end
 
-  # Return the pitch's frequency, which is determined by multiplying the base 
+  # Return the pitch's frequency, which is determined by multiplying the base
   # frequency and the pitch ratio. Base frequency defaults to DEFAULT_BASE_FREQ,
-  # but can be set during initialization to something else by specifying the 
+  # but can be set during initialization to something else by specifying the
   # :base_freq key.
   def freq
     return self.ratio() * BASE_FREQ
   end
-  
-  # Calculate the pitch ratio. Raises 2 to the power of the total semitone
-  # count divided by semitones-per-octave.
+
+  # Calculate the pitch ratio. Raises 2 to the power of the total cent
+  # count divided by cents-per-octave.
   # @return [Float] ratio
   def ratio
-    2.0**(@total_semitone.to_f / SEMITONES_PER_OCTAVE)
+    2.0**(@total_cents.to_f / CENTS_PER_OCTAVE)
   end
-  
+
   # Override default hash method.
   def hash
-    return @total_semitone
+    return @total_cents
   end
-  
+
   # Compare pitch equality using total semitone
   def ==(other)
     return (self.class == other.class &&
-      @total_semitone == other.total_semitone)
+      @total_cents == other.total_cents)
   end
-  
+
   def eql?(other)
     self == other
   end
-  
+
   # Compare pitches. A higher ratio or total semitone is considered larger.
   # @param [Pitch] other The pitch object to compare.
   def <=> (other)
-    @total_semitone <=> other.total_semitone
+    @total_cents <=> other.total_cents
   end
-  
+
+  # rounds to the nearest semitone
+  def round
+    if @cent == 0
+      self.clone
+    else
+      Pitch.new(semitone: (@total_cents / CENTS_PER_SEMITONE.to_f).round)
+    end
+  end
+
+  # diff in (rounded) semitones
   def diff other
-    @total_semitone - other.total_semitone
+    Rational(@total_cents - other.total_cents, CENTS_PER_SEMITONE)
   end
-  
-  def transpose interval
-    Pitch.from_semitones @total_semitone + interval
+
+  def transpose semitones
+    Pitch.new(cent: (@total_cents + semitones * CENTS_PER_SEMITONE).round)
   end
-  
-  # Produce an identical Pitch object.
+
   def clone
-    Marshal.load(Marshal.dump(self))  # is this cheating?
+    Pitch.new(cent: @total_cents)
   end
-  
+
   def to_s(sharpit = false)
     letter = case semitone
     when 0 then "C"
     when 1 then sharpit  ? "C#" : "Db"
     when 2 then "D"
@@ -99,37 +115,41 @@
     when 9 then "A"
     when 10 then sharpit  ? "A#" : "Bb"
     when 11 then "B"
     end
     
-    return letter + octave.to_s
+    if @cent == 0
+      return letter + octave.to_s
+    elsif @cent > 0
+      return letter + octave.to_s + "+" + @cent.to_s
+    else
+      return letter + octave.to_s + @cent.to_s
+    end
   end
-  
+
   def self.from_ratio ratio
     raise NonPositiveError, "ratio #{ratio} is not > 0" unless ratio > 0
     x = Math.log2 ratio
-    semitones = (x * SEMITONES_PER_OCTAVE).round
-    from_semitones(semitones)
+    new(cent: (x * CENTS_PER_OCTAVE).round)
   end
-  
+
   def self.from_freq freq
     from_ratio(freq / BASE_FREQ)
   end
-  
-  def self.from_semitones semitones
-    Pitch.new(semitone: semitones)
-  end
-  
+
   private
-  
-  # Balance out the octave and semitone count. 
+
+  # Balance out the octave and semitone count.
   def normalize!
-    semitoneTotal = (@octave * SEMITONES_PER_OCTAVE) + @semitone
+    centsTotal = @total_cents
     
-    @octave = semitoneTotal / SEMITONES_PER_OCTAVE
-    semitoneTotal -= @octave * SEMITONES_PER_OCTAVE
+    @octave = centsTotal / CENTS_PER_OCTAVE
+    centsTotal -= @octave * CENTS_PER_OCTAVE
     
-    @semitone = semitoneTotal
+    @semitone = centsTotal / CENTS_PER_SEMITONE
+    centsTotal -= @semitone * CENTS_PER_SEMITONE
+    
+    @cent = centsTotal
     return self
   end
 end
 
 end