I've used this trick when I've had to deal with mocap, but find it's really useful for trying out a new take in an animation, especially one that's a bit overworked. Once there's a lot of keys down, it can be hard to be courageous and really make strong decisions regarding posing and timing for fear that you'll lose the work you have. This can be counter to doing good animation, since poses and timing can ALWAYS be strengthened and improved.
I'm not sure how widely known this technique is, since I just stumbled upon it myself, but in case it's of use to someone, I thought I'd post it.
This sea of data is counter to any kind of keyframing, and reducing it manually is very slow, however Maya now has animation layers.
Let's start by grabbing all our control objects (selection sets are good for this sort of thing) and clicking the anim radio button.
Still with me? With your controls selected, click that blue sphere with a cryptic yellow star. This allows you to key these objects on a new layer.
Now I'm going to go through the animation and stamp down the keys I want. In a way, reverse engineering keyframing over our mocap. When we're done, turn the weight back to 1. This kills a lot of detail in the animation, but if recorded in an artful manner, saves the right keys.
That's it in a nutshell. Now if you play the animation, it's more clear, easier to see the main beats, and easier to retime and alter key poses.
This is also useful for revising sections of your animation. Do the above setup, but set a zero key 1 frame before you begin altering the animation, then weight to 1, then grab frames, set a weight to 1 key, then a zero key and you're good to go.
clips to come.