# Recipe 66: Half the frequency

def half(filename):
  source = makeSound(filename)
  dur = getLength(source) / getSamplingRate(source)
  dest = makeSound(filename)
  #dest = makeEmptySound(int(dur + 1))

  srcSample = 1
  for destSample in range(1, getLength(dest)+1):
    volume = getSampleValueAt(source, int(srcSample) )
    setSampleValueAt(dest, destSample, volume)	
    srcSample = srcSample + 0.5

  #play(dest)
  return dest