Apple Motion 4 - Manual (Page 429)

Combining Behaviors and Keyframes in the Keyframe Editor
When you display a parameter that’s affected by a behavior in the Keyframe Editor, two
curves appear for that parameter. An uneditable curve in the background displays the
parameter as it is affected by the behavior. There are no keyframes over this first curve.
Superimposed over the curve displaying the behavior’s effect is the parameter’s editable
curve.
Behavior effect curve Editable curve
You can keyframe a parameter either before or after applying a behavior to the object
that affects it. When you keyframe a parameter that is already affected by a behavior, the
value of the keyframed curve is combined with the value generated by the behavior at
each frame, which either raises or lowers the resulting value displayed by the background
curve. The background curve doesn’t just display the behavior’s animated values, it
displays the sum of all values affecting that parameter.
Behavior curve is affected
by the keyframes.
429 Chapter 9 Using Behaviors