lib/head_music/octave.rb in head_music-0.19.0 vs lib/head_music/octave.rb in head_music-0.19.1

@@ -37,7 +37,15 @@
 
   def <=>(other)
     to_i <=> other.to_i
   end
 
+  def +(other)
+    self.class.get(to_i + other.to_i)
+  end
+
+  def -(other)
+    self.class.get(to_i - other.to_i)
+  end
+
   private_class_method :new
 end