Regarding this circuit I found on www.geofex.com detailing the famous Tube Screamer guitar pedal
(source: geofex.com)
I don't understand the purpose of the BJT input emitter follower transistor. If it was to increase the input resistance of the pedal then the TL072 would have much greater input impedance than a BJT no? (I read approximately 10^12 in the datasheet for TL07x)