code: def _synthesize_multiple_subprocess(self, text_file, output_file_path, quit_after=None, backwards=False):
          
          self.log(u"Synthesizing multiple via subprocess...")
          ret = self._synthesize_multiple_generic(
              helper_function=self._synthesize_single_subprocess_helper,
              text_file=text_file,
              output_file_path=output_file_path,
              quit_after=quit_after,
              backwards=backwards
          )
          self.log(u"Synthesizing multiple via subprocess... done")
          return ret
docs: Synthesize multiple fragments via ``subprocess``.
  
          :rtype: tuple (result, (anchors, current_time, num_chars))