E R R O R... E R R O R... E R R O R...

Sorry, I have to start again...
The way it looks, I need to reveal "the whole, boring story" how I want to apply this switch/ switches.

It's actually not a footpedal, but a knee lever control, which has to do with www.live-styler.de PC Key Control 244/245. Confusing and boring, I know!

Now it allows me to switch the YamahaStyles accompaniment via 2 switches (from the PC-Keyboard) from major to minor or 7th chords.

The trouble is that when I want to switch the accompaniment from major chord to minor or 7th chord, I need to press the PC switch another time to cancel the previously chosen minor or 7th chord, before I can switch back to a major or over to a 7th chord.

I hate that, because there's no time for it; also it would be pretty confusing.
That's why I want to only have to press the knee lever once for either minor or 7th and when I release (or don't touch) the lever, the lever stays invariably in (the center) major chord position.

I also just realized that my previous mechanical switch was wrongly drawn, because PC-Kbd keys can only be momentarily switched!! (i.e. cannot be continuously activated or the key repeats, such as: "aaaaaaaaa etc."!)
That means: first, when I press the knee lever the PC-Kbd key has to be briefly activated (to turn on the effect) and when I release the knee lever, the same PC-Kbd key has to be another time briefly activated (to turn off the effect). Here's my sunshine solution:



Life isn't meant to be easy!!!

 

This is the solution I told you right? Is it working well?

 

Yes... (and no), because you wrote:

Ok connect the input voltage to the common of the switch, connect the normally open contact to the effect and then connect the normally closed contact to the normally open contact. With the switch you show it should turn off when you release the pedal.

But at that time I still didn't take into account that the PC-Kbd key can only be momentarily switched!! (i.e. cannot be continuously activated or the key repeats, such as: "aaaaaaaaa etc." and nobody mentioned it either... just by sheer coincidence it came to my attention.
So, in fact I'm glad this seemingly big problem turned out to be amazingly simple and I thank you all for having kicked me to success.
The thing I'm still worried now is: how to connect 4 tiny wired to two keys of my lousy China PC-Kbd? ... Yes, life isn't meant to be easy!

 

Hurray!!!
You won't believe it, but I successfully connected the two PC-Kbd switches with two wires on each key. I was a watchmaker job!
I unscrewed the cheapo-China Kbd and then measured the connection between key contact pad and the terminal to the chip of the two plastic circuit layers.
The hardest was to solder hair-thin wires onto the
crowded, narrow tracks to the chip.
I used a low heat solder iron with a fine tip, pre-soldered the wire as well as the track and then just quickly soldered them together.
Now I have got a plug with 4 terminals on the keyboard hanging and it works a beauty!
So, my 45 years of hobby electronics fiddling experiences payed again off.

I wished I could buy a conductive glue. I have to search the Internet for it. Maybe there exist such a thing?