Jittering location in animation I'm trying to jitter an object's location during an animation, and be able to control the strength of the hitter. I tried keyframing the strength of a noise f-curve modifier, which doesn't work:

Failed to resolve path to property, try manually specifying this using a Keying Set instead


Is there a good way to jitter the location of an object, and change the strength of the jitter throughout the animation?
In this test scene: 


the empty has the original animation 
the cube copies the empty animation and adds some random value 
the amplitude of the random value is controlled by cube property :


this is the driver of the X_loc of the cube :



this is the animation while changing the cube property :