Open a song and play it for a while.
Then stop playing.
Go to Tools->Settings and configure to an other Midiport
Try to play the same open song again.
The result is that you have no sound.
You must close the application to get sound again.
I find a solution for this bug.
In the file TuxGuitar\src\org\herac\tuxguitar\app\system\config\items\SoundOption.java I added in method applyConfig after line 152 the following:
Now you can switch to other midiports and have sound when you play the same song.
Your change in MidiPlayer.java (Version 1061) works fine.