Animate a box ...

Ctlr Alt left click changes begin frame

Ctrl Alt right click changes end frame

You can move key frames ... you can also copy them with shift drag.

If you have a sound track, you can see it ... right click the time line ...

If you shift drag to copy keys, you will get a linear interpolation, which is good to keep feet from moving around, etc.

You can scale keys ... it works by scaling from the position of the track bar ...

you can even reverse scale and play backwards

The dotted line is outside of the range of the curve ...

Play with the various out of range types ...