Okay, now I'll try to explain this better way.
This is another similar situation, but not exactly the same as I said in my first message:
When an object falls to object that is in the Family named PhysicsObjects, I want it to create a particle cloud. There are two examples of those clouds: "Dust" and "MusicParticles".
The event works perfectly in a situation when an object falls to any object in the Family except when the situation is like "piano is falling on piano". That event cannot somehow understand that it can itself also be part of that family... In that case the particles never appeared until some different object falls to that piano.
The last event in that picture is my try to create it for the piano with sub event, but it did not work either and I do not know why.
BTW: Volkiller730, thx for helping with the subgroup. I installed your cave game and its very similar as this game I am trying to do.