Spline Animation?

I am relatively new to animation. I read in the docs about spline animation, but find no explamaition of what it is or how to use it.

Also, the docs say that you can use envelopes to set up shape animation, so you could use bones or whatever deformers to achieve a shape and then simply create a shape key. THe docs say that you should mute the envelop or the deformer before storing the shape key. Logically when I mute the envelope or deformer, the shape returns to its reference shape and the deformer has no effect(as if it was deleted)
So I am having trouble seeing exactly how this would be achieved.If anyone can help, please tell if the process would be the same for envelopes and deformers(such as spine curves to drive facial shapes)

Gracias Muchachos

make sure your envelope operator is below your shape combiner operator. that way it wont be assimilated into your shapes each time you make them.

I store shapes rather than save shape keys, that way it wont automatically bring your shape into the mixer (and potentially colour subsequent shapes).

that help?
_sam