Most guitar pedals obtain a high input impedance simply by using a large resistor at the input of the first opamp, but this generates a good deal of noise due to the input bias current. The Glass Blower avoids this by using a smaller resistance (R2) which is bootstrapped by C2 to an effective value of tens of megohms.
Correction
September 22, 2010.
On the component layout of the PCB designed by the author (free download # 100165-11.zip), transistor Q2 (2N3906) should be turned 180 degrees.