Hi there, thanks for your comment and it was probably my fault for not making it particularly clear. Yes that is exactly what the pedals and levers do, some pull the strings to increase the tension and pitch while others (in particular the knee levers) slacken the tension on some of the strings.

I am starting to think it is perhaps more difficult to explain that to play! I plan to do an addendum to that video showing a closeup of the actual mechanics.

It was probably that warm feeling that got me addicted in the first place!