Can anyone tell me how to set up a neck on character that has to
be expandable like an accordian? Basically what I have is a nurbs neck built like an accordian with a sphere head. I put bones inside the neck and then set up an IK Spline on that. Then I skinned the neck to the skeleton. I selected the cv's on the spline and clustered them and made nurbs circle controls for each of the four clusters and parented those to each cluster. Then I grouped the sphere head to itself and point constrained that to the top joint of the skeleton.

Now it moves side to side or all over when you grab any of the controls BUT how do I get it squash or stretch like an accordian? Someone suggested a set driven key.

I want the head to stay with the neck where they meet but also be able to freely rotate the head and animate it too of course.

It would be like a duck like character let's say, but with a more accordian neck that can expand and contract. Also I would like the base/bottom of the neck to remain stationary and not bend or deform when other parts are bent.

Any ideas??

Here is an idea of what I've done so far. This isn't the real one I'm doing, but I can't share that at this time.