The JavaSound demo retrieves an array of MidiDevice.Info's from MidiSystem.getReceiverInfo().  Then it graps the receiver with MidiSystem.getReceiver(info[i]).  The description from each one of the MidiDevice.Info's are put into the options menu.  The user can select from one of the menuitems to change the receiver.  The receiver is passed to the open() method to each one of the demo tabs upon tab changes and menuitem selection.  Here's the implementation details :

    public void open(Receiver receiver) {
        sequencer = MidiSystem.getSequencer(null);
        if (receiver != null) {
            try {
                sequencer.addOutReceiver(receiver);
            } catch (Exception e) { e.printStackTrace(); }
        }
        ...
    }

Nothing appears to change when selecting from the four different receivers that appear in the options menu on my PC.

/usr/local/java/jdk1.3/win32/demo/sound

java version "1.3.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0-F)
Java(TM) HotSpot Client VM (build 1.3beta-F, interpreted mode)