Both the v67 and C1 use FET's according to their specs.
If I can remember back to a time when my brain was functioning, I believe you can think of a FET as a voltage controlled variable resistor. It has an exremely high input impedance, and I assume is used to couple (impedance match) the voltage changes of the condenser (capacitor) to the next stage of the internal mic preamp for subsequent amplification.
The same function can also be performed by a vacuum tube, and probably by suitable discrete bipolar, op amp or other integrated circuits.
Let me add I've enjoyed lurking in this forum for the last several months, and have learned a considerable amount of fact and opinion, though sometimes it's a little difficult for me to separate the two.