Commodore VIC-20 User Manual page 243

Chapter 7: Sound
229
To turn off the sound, you can use any of the following methods:
· POKE 0 into the tone register
• POKE 0 into the volume register
· Simultaneously press
RUN/STOP
and
RESTORE.
The first method puts a nonexistent tone value into the tone register.
Actually, any value lower than 128 would accomplish this.
The second method turns the volume register to the minimum position,
which is off.
The third method resets the system and therefore resets all system
variables, such as the tone registers, screen and border colors, and so on. It is
better to use one of the first two methods, since the third method may do
more than you had in mind.
Noise Register
The fourth sound register (memory location 36877) controls a noise
generator. The sound created by this register can vary from a high-pitched
hiss
POKE
36878/15
POKE
36877/254
to a low roar.
POKE 368771128
Once again, to turn off the sound, you can use
POKE
36878/8
which turns the volume down, or
POKE
3687118
which puts an invalid number into the tone register.
By putting different values into this register and combining the sounds
with the tone registers, it is possible to create a wider range of sounds than
can be produced using the tone registers alone.