OK, can't draw it now, but the configuration is 1/6 40106 configured as a variable frequency oscillator. R is a 1M pot, and C is a 0.22uF capacitor.
The output of this is connected to 1/4 4066 do that it switches the input signal on and off.
Essentially it amplitude "modulates" the input with a 50% duty cycle square wave.
I wouldn't be surprised itf it also removes some of the negative peaks of the input signal due to the effects of the input protection too.
I'm surprised it doesn't sound like complete crap!
edit: oh there are a heap of inputs left floating which is a bad thing.