Use the Edit Time tools to work directly with selected blocks of time in the Dope Sheet Editor, as opposed to working with keys and range bars. A block of time is any contiguous time segment, across one or more tracks, and is independent of key locations.
Enter Edit Time mode by selecting a time segment in the Dope Sheet Editor. Once a time segment has been selected you can insert, cut, copy, paste, or reverse the time segment, including its keys. The time tools are available from the Time menu and the Time Toolbar. Time tools are unavailable from the Time menu in Edit Ranges mode.
Use Cut Time to delete a block of time from one or more tracks and place it in the clipboard. Before you can paste time in a track, you must have time in the clipboard. After specifying a block of time, place it in the clipboard with Cut Time or .
Reverse Time flips the order of keys within the selected time. You can reverse time by scaling a selection past its left edge, but this also changes the position of the selection and the remaining keys around it. Use Reverse Time to reverse keys within a designated block of time.
Scale Time scales a block of time. You can scale down to fit into less time, or expand it to fill more time. Scale Time doesn't use the Track View time slider as the scale origin reference; it always scales from the first frame of the key selection.
If you paste the same block of time repeatedly, one block following the other, you can create a looping segment in your animation. To create a smooth looping animation, you need to exclude either the first or last key of the copied block to prevent keys from doubling up at the ends.
Use Reduce Keys to decrease key density. Animating with inverse kinematics, or creating any complex animation, can result in many keys, which can make editing the animation difficult. In the case of applied inverse kinematics, 3ds Max generates a key on nearly every frame. Often, the same animation can be produced with fewer keys. Having fewer keys in a track makes it easier to change your animation.