Vintage Synth Repair

Hi all, this is my first message here: I'm thrilled by analog circuits 
although I'm not an expert, so I'm studying the Yamaha CS80 to try and 
make some sort of virtual, as I'm not satisfied with the Arturia.

I would ask you some questions to the people here who knows more than 
me about reading schematics

First question: if you look at the picture I posted there

http://f1.grp.yahoofs.com/v1/YIrqSApHmjS6cA3dqhZH-
GmV76P2YcikZA_XszBHjYyz7poNC3SZztKSOwD4kC4LWbNppnry_1movZzpGN2mUqumJOKHG
p_Ipg/CS80%20schems/tws.jpg

You will see the velocity generator in Yamaha CS80: I'd like to know 
this: what is the FET doing here? And, what is the output of 
the "Initial touch"? Is it a decay envelope? How does it link to a 
supposed variable gate velocity?

Now look here

http://f1.grp.yahoofs.com/v1/YIrqSFqjXlS6cA3dBH1N34CSLYoZ5oUQzDqtOY18kaL
q4napy2NIUcZliGnwlKUQlnbxNbPxLmA0pd3mVL77desKCsG_EsLsbQ/CS80%
20schems/41%2520-%2520M%2520Circuit%2520Diagram.bmp

You will see that I highlighted in red two resistors, one set at 100k 
to the HPF and the other set at 47k : do these resistors act as CV 
limiters? And what is more limited, the HPF or the LPF?

Hope these questions are not too hard, thx for any reply