code: def start(self, driver=None):
          
          if driver is not None:
              assert driver in [
                      'alsa',
                      'oss',
                      'jack',
                      'portaudio',
                      'sndmgr',
                      'coreaudio',
                      'Direct Sound',
                      'dsound',
                      'pulseaudio'
                      ]
              fluid_settings_setstr(self.settings, 'audio.driver', driver)
          self.audio_driver = new_fluid_audio_driver(self.settings, self.synth)
docs: Start audio output driver in separate background thread.
  
          Call this function any time after creating the Synth object.
          If you don't call this function, use get_samples() to generate
          samples.
  
          Optional keyword argument:
            driver: which audio driver to use for output
                    Possible choices:
                      'alsa', 'oss', 'jack', 'portaudio'
                      'sndmgr', 'coreaudio', 'Direct Sound',
                      'dsound', 'pulseaudio'
  
          Not all drivers will be available for every platform, it depends on
          which drivers were compiled into FluidSynth for your platform.