def lowshelf(self, gain=-20.0, frequency=100, slope=0.5):
        """lowshelf takes 3 parameters: a signed number for gain or attenuation
        in dB, filter frequency in Hz and slope (default=0.5, maximum=1.0).

        Beware of Clipping when using positive gain.
        """
        self.command.append('bass')
        self.command.append(gain)
        self.command.append(frequency)
        self.command.append(slope)
        return self
lowshelf takes 3 parameters: a signed number for gain or attenuation
        in dB, filter frequency in Hz and slope (default=0.5, maximum=1.0).

        Beware of Clipping when using positive gain.