Hi,
I have just updated this page:
http://pianobooster.sourceforge.net/faq.html#how-do-i-hear-the-sound-on-linux-ubuntuI hope that helps. If you add midifile onto the end of the very long fluidsynth line it should play the midifile which will prove that fluidsynth is working OK.
Also watch out for the error message:
fluidsynth: error: The "plughw:0" audio device is used by another application
If this happens then try to closing everything else that may be using the sound.
Please let us know how you get on.
Louis