EMS Diode Filter Qestion

[Christopher_List at Sonymusic.Com]

  Can anyone explain why the input to this filter is set up the way it is?

  You've got the initial level and the CV being pseudo-summed by a
  non-inverting op-amp with gain of 1.33 - then the output of that goes to
  an inverting op-amp with gain of .5 - and the output of that opamp goes
  to the circuit.

  What's the purpose of the first op-amp? Is there somesort of old-school
  circuit design trickery here?

  - Thanks,
  Chris