All parts under keyboard control will sound simultaneously but when you turn off keyboard control for one of the parts you are effectively disconnecting it from the other parts in the performance so only that part will sound. If you touch the name of any of the remaining parts, all remaining parts will sound simultaneously as they are all still under keyboard control - you of course will not hear the part that you have turned keyboard control off for as it is no longer under keyboard control.

Try to think of this as though you have multiple synths joined together and whilst they are under keyboard control you can play all of them from any of them but turning off keyboard control disconnects it from the total so it can only play itself.

(Sorry that I had to say keyboard control so many times)!

We cannot be sure if this is a BIG PROBLEM or no problem at all. Can you give specifics - does this happen on every sound?

Let's say your playing "Seattle Sections" it has seven Parts... You touch the green KBD CTRL icon to turn off Part 7
You report a BIG PROBLEM because now no sound is happening.

It's not a problem because you selected Part 7 to play by highlighting Part 7, but because Part 7 only fades in when the Super Knob is turned up, you wrongly conclude the sound is broken or there's a bug. But it's not.

Try the "CFX + FM EP" you turn off KBD CTRL by touching the green KBD CTRL icon in Part 5. You have selected a Part that is off until the Super Knob is turned up. I think you are just inheriting things you are not aware of... Play with it bit more, and let us know. If you cannot figure it out, please provide which Performance and we'll try to explain what is going on.

Exatly Phil, but for me this is a bug, because if I have 5 parts and I turn of the keyboard switch off one part, it is logic that the other 4 parts continue to sound instead be muted. There is no logic in a way to turn off one switch and obtain that 5 part don't sound.

There is a difference between KBD CTRL and MUTE, you have not discovered a bug, only the difference in use. You didn't want to turn Off KBD CTRL, you wanted to Mute a Part.

[PERFORMANCE CONTROL] lights
This turns the second row of right panel buttons into PART MUTES 1-8.

I know about mute, but I try to use keybord switch because I wanna that a drum track with arpeggiator stop to sound the arpeggio.
If I stop the arpeggio with "arpeggio switch" the drum sound because the keyboar control the drum part and I don't want that the drum sound when I stop the arpeggio. So I try to workaround this problem only switch off the keyboard for drum part, but it happens that all parts will be muted and I think (maybe wrong) that is is a bug because if I touch the name of the perormance the oter part start to sound again (because it is logic that if I switch off only one part the other should sound). So in the and I think that the behevior of montage in this case it is not logic. If I switch off one part the other dont's sound untill I touch the program name.....it have no logic sense.

I think you are still not grasping what keyboard control does. When you press the keyboard control buttons of a part which deselects it (the icon goes from green to grey) you'll notice that the Part Select button on the right for that part number will light up and a box will be drawn round that part on the screen. In other words you have isolated that part and as you have turned keyboard control off for that part it can no longer communicate with the other parts in the performance which is why you can't hear them - they are not actually muted they just can't be controlled from the part you are on. When you press the performance name the Part Select light goes out so that any parts under keyboard control will play together as you are not selecting an individual part.

I don't know if that makes it clearer?

This point is clear Phil but don't help me :--) Anyway thanks.