So I was having a little read about speaker.drv over on this older topic:

Can DOSBox make noise thru the real PC speaker?

And I noticed that the statement "the driver STOPS all processes".

Now thinking of games like commander keen where sound is made when you step, and I can understand as it makes sounds between each frame and since the game is low fps anyway it wouldn't be a stretch.

But how does Bubble Dizzy do it? It has pc-speaker music, and it's often the game I put on to show off my ol' Compaq in its beep-happy state.