the theory is you don't want the LED spending time completely on or completely off. so you set the trim pots so the lamp is always getting brighter or dimming since those are the changes that affect the sound.
No problem there...
I do notice that power to IC6A&B is only 8.3V/-7.4 while on all other 072s it is 9V/-7.4V
also, I mounted my LDRs Lower than most people I see build pics from... Could that be a problem?