8.  VDU7 bleep
    ~~~~~~~~~~
You can alter the nature of the VDU7 'bleep' as follows. *FX210,1 turns it
off, and *FX210 turns it on again. You can alter the pitch with *FX213,P
where "P" is a number from 0 to 255, (default value is about 100). Similarly,
you can alter the duration with *FX214,D (default value about 7). You can
change sound channel or 'voice' with *FX211,N where "N" is 0 to 3, (normally
3). Thus, if you try *FX211,0 you will get a sort of explosion noise, and
*FX211,3 will restore it to a bleep. You can test the bleep by pressing
<Ctrl><G> ; quicker than typing VDU7.