Using method_missing properly by calling `super`

method_missing_super.rb

# This snippet is taken from:
# "The Polite Programmer's Guide to Ruby Etiquette" 
# http://bit.ly/hrwdPY

class BlackMagicStereo < Stereo
  def method_missing(name, *args)
    if sym.to_s =~ /^play_(\w+)$/
      system("open songs/#{$1}.m4a")
    else 
      # Here, very important! 
      # Don't forget to delegate up to previous implementation
      super 
    end
   end
end

stereo = BlackMagicStereo.new
stereo.play_back_magic_woman # This works
# This fails if you don't call `super` 
# Because it's defined somewhere in the inherited classes 
stereo.play("Magic Bus")