Java Midi音序器会在数次后停止发出声音。如何调试/解决？

private Sequencer sequencer ;
...
void play(Sequence sequence) {
    sequencer.open() ;
    sequencer.setSequence(sequence) ;
    sequencer.start() ; // plays sequence
    sequencer.close() ;
}

public void play(Sequence sequence) {
    sequencer.setSequence(sequence);
    sequencer.stop();
    sequencer.setTickPosition(0);
    sequencer.start();
}