public void play() 
    {
        // Play the midi file if it is open, and if the squencer is not already
        // playing.
        if ( !isFileOpen ) {
            System.err.println("Cannot play.  Midi file not loaded.");
            return;
        }
        if ( sequencer.isRunning() ){
            System.err.println("Cannot play.  Already playing.");
            return;
        }
        
        // Start the sequencer to start playing.
        sequencer.start();
        
    } // End play()