Note: Here I only show the complete connection of accordion button C.
Each gate (ins 5, 6, 12, 13) has a 22K pulldown resistor to ground.
The are 2 groups ( groupMinor IC1 to IC3) and group7th IC4 to IC6)

Pressing accordion button C sends +5V to SW pin 4 of IC1 and when I press Minor foot switch +5V are send to all gates of IC1 to IC3
Result: I get a chorus of all switches on from IC1 to IC3, because all 12 gates (of IC1 to IC3) are activated via foot switch. Yet, I only wanted to have C and a# activated via the accordion button C and Minor foot switch.
What am I doing wrong?

 

We have your diagram. What is your question?

hgmjr

 

Sorry I wasn't ready yet. I added the diagram first to see if it appeared...
Now it's complete!

 

Is there a question?

 

The question was/ is: What am I doing wrong?

The problem is that I need to control each group via a foot switch; i.e. one foot switch for the Minor group (IC1 to IC3) and one foot switch for the 7th group (IC4 to IC6).
That's why I thought to connect e.g. the 12 gates of the Minor group together to a foot switch to activate the desired gate. Yet, that also allows the other 11 gates to float (away from ground), causing them to wrongly activate their gates...

The good thing on this circuit is that only +5V is switched.
There must be a way of doing it with diodes and resistors, instead 4066B? Using the resistors to earth out the signal from either group, because the same accordion C button serves both (Minor & 7th) groups, but shall only serve one group at a time! How to do it?