SOUND freq [, dur]
Generate a single tone of ‘freq’ (between 20Hz and 1MHz) for ‘dur’ milliseconds. The sound is played in the background and does not stop program execution.
If ‘dur’ is not specified the sound will play forever until turned off. If ‘dur’ is zero, any active SOUND statement is turned off.
The command has been replaced with the TONE command that generates a pure sine wave (not a square wave).