With my travel to the development lab Munich, I discovered, that the immersive piano model is located much too high, if you are sitting in front of the immersive space.
This was definitively something I could not see inside the simulator. The visionOS simulator obviously assumes that the user is standing in front of the scene. But possibly most users want to sit in front of the piano model, while listening and watching.
So I will try to resolve this issue as soon as possible, providing an update.