I see we have an Intellivison fan here. Great rendition of Shark! Shark!

Nahh, i first saw this type of game at:
http://www.xgenstudios.com/play/fishyclassici assume your refering to some old 8bit console

I'm not quite sure what you mean by "the music judders"? If you're asking why it stutters, the answer is that it doesn't.
It does for me(on winxp/2000 jre 1.4/1.5), maybe you just cant tell, but without the music its alot smoother and faster.
you sure ur not using the sound bank? (which isn't allowed)
It doesnt need a soundbank as it uses applet.AudioClip
i have updated it with a new version where the music stops when the stop() method is called.