Here is my understanding so far.
The first 100Kohm pot is the gain control. The first transistor clips the signal a little or a lot dependent on the gain. The output (collector) of the first transistor feeds the clipped signal into the second transistor which clips the signal even harder. Again the signal leaves the transistor through the collector and is fed through a low pass filter, the cutoff frequency dependent on the 50kohm pots wiper. After passing through the filter the signal is routed through to the output, passing over a potentiometer which controls over all volume/amplitude of the signal by adjusting the 100kohm pot wiper.