How to connect two func_instances?
Thanks for your tipps but the problem seems to be much easier than I thought. I solved it this way:
The turret in the func_instance will react by OnPickUpPhysGun and the Target Entity for my unknown music_instance has the name $music.
My music_instance has a name with an @ in my map. Then I put the name (with the @) into the parm_field of my turret_instance which replaces the $music and everything works. That's the customization I want. =)
Maybe your gave me the solution on a plate but I didn't see it. =/
that is that i try to say 
Oh good, well I'm not at the end. ^_^
Is there a way to set the "FLAG" of an entity by a func_parms field? It would make things a lot easier than what I do actually. =/
Which kind of Flag do you mean? ^^
He means a spawnflag. And there is, but it's really difficult and requires editing your FGD files and doing bitwise arithmetic every time you make the instance. Trust me, it's not worth it.