def check_cached_spectrogram_paths(file_name, source_existing, target_possible, modify_parameters)
          target_existing_paths = @spectrogram_cache.existing_paths(modify_parameters)
          if target_existing_paths.blank?
            msg = "Could not create cached spectrogram for #{file_name} from " \
                  " #{source_existing} in #{target_possible} using #{modify_parameters}."