code: def _get_channel(self):
          
          if self.channel is None:
              # Get default channel as the first one that pops up in
              # 'amixer scontrols' output, which contains strings in the
              # following format:
              #
              #     Simple mixer control 'Master',0
              #     Simple mixer control 'Capture',0
              out = check_output(['amixer', 'scontrols']).decode()
              m = re.search(r"'(?P<channel>[^']+)'", out)
              if m:
                  self.channel = m.group('channel')
              else:
                  self.channel = 'Playback'
  
          return self.channel
docs: :returns: The detected sound channel
          :rtype: string