Resolved Is it possible to move one rig-bone during animation?

Hello, I do have a humanoid character, that repeatedly plays an animation, where it moves the arms around. I now want to manually control the head with the keyboard using a script to set the rotation based on keystrokes.
This works only if the animation is not playing. While the animation is playing, the head is not moving... How do I do this correctly?

Thanks for a hint.

 

My fault. I forgot to create the animation rig with this one....