I'm posting this question on this stack-exchange site, because it appeared to be the one made for this kind of questions. If this happens to not be the case, I'm sorry, I didn't know better. Also forgive me any issues with terminology (or point them out to me), I'm not an engineer.
I want to build a music instrument (I won't go into details here, because I think it's not necessary). In this instrument there will be keys (in the picture I drew, the keys are the blue boxes, as seen from above. The Black arrows indicate the directions in which the keys are movable). If a key is pressed (which means "moved up" in the picture), I want a little string to be pulled. The rope is drawn with black color, and one can see the way it is attached to the keys. The red circles are supposed to be the bars that will press the string out of its equilibrium position.
In the picture, the middle key is pressed, and the string is elongated because of this.
My question is: What materials should I use for the string AND the bars, to make the string glide on the bar as friction-less as possible?
Some additional information:
There will be 20 keys, and the distance they move, if they are pressed, is 5 millimeters. The string can't be thicker than a thick guitar string.
My initial thoughts were to use fishing line, and make the bars out of brass. But maybe there are better options to use.
The string isn't vibrating, and it won't be the thing to be responsible for the sound. Maybe I should have written "rope" instead of string. The purpose of the strings seen is to activate a little switch, when the key is pressed. To accomplish this, as the keys are pressed (and move), the string will be elongated, as it slides over the red bars. The ellongated string then pulls a little switch.
It is to say that there is some tension on the string (the switch effectively raises one of the vibrating strings, so the force acting on the non-vibrating strings is roughly the same force it takes to pull a guitar string out of its equilibrium position).