docs: def midi2f(params, midi=69):
      '''
      Convert a midi value to a frequency.
      Midi value 69 corresponds to A4 (440Hz). Changing the midi value by 1 corresponds to
      one semitone
      :param params: buffer parameters, controls length of signal created
      :param midi: midi value
      :return: array of resulting frequency
      '''
      midi = create_buffer(params, midi)
      output = 2**((midi - 69)/12)*440
      return output