You can edit existing animation non-destructively with adjustment layers in the Layer Manager. Animation that can be affected with adjustment layers includes CATMotion, absolute keyframe animation, motion capture data, and even other adjustment layers.
Keyframes in an adjustment layer offset the existing animation. For example, you could use an adjustment layer to control the head movements of a rig walking with CATMotion. The head animation is applied on top of the existing CATMotion animation.
CAT offers two types of adjustment layers: local and world. Local adjustment layers are useful for offsetting the rig element relative the to rig (for example, inclining the head). World adjustment layers are useful for offsetting IK targets, such as for a foot, in a motion-capture sequence.
A Local Adjustment layer offsets animation in the local coordinate space of the rig.
To create a Local Adjustment layer:
Select any part of the rig.
Motion panel, go to the Layer Manager rollout.
In the layers list, highlight the Available item if necessary.
(Abs) until the flyout opens, and then drag down to 
(Add Local Adjustment Layer) and release the mouse.
3ds Max creates a new layer below the existing layer.
This new layer is active and is weighted to 100%, meaning that you can start tweaking your animation immediately.
The World Adjustment layer offsets the animation in world space.
To create a World Adjustment Layer:
Select any part of the rig.
Motion panel, go to the Layer Manager rollout.
Make sure Available is highlighted in the Layers list.
(Abs) until the flyout opens, and then drag down to (Add World Adjustment Layer) and release the mouse.
3ds Max creates a new World Adjustment layer below the existing layer.
This new layer is selected and weighted to 100%, meaning that you can start tweaking your animation immediately.
