code: protected boolean enqueue (SoundKey key, boolean okToStartNew)
      {
          boolean add;
          boolean queued;
          synchronized (_queue) {
              if (key.cmd == PLAY && _queue.size() > MAX_QUEUE_SIZE) {
                  queued = add = false;
              } else {
                  _queue.appendLoud(key);
                  queued = true;
                  add = okToStartNew && (_freeSpoolers == 0) && (_spoolerCount < MAX_SPOOLERS);
                  if (add) {
                      _spoolerCount++;
                  }
              }
          }
  
          // and if we need a new thread, add it
          if (add) {
              Thread spooler = new Thread("narya SoundManager line spooler") {
                  @Override
                  public void run () {
                      spoolerRun();
                  }
              };
              spooler.setDaemon(true);
              spooler.start();
          }
  
          return queued;
      }
docs: Enqueue a new SoundKey.