Rigging when bones must achieve conflicting goals

Question

I have a question and words seem to fail me when searching here for an answer. Although this is related to a swim cycle, it is a problem I have encountered before: How do I achieve more than one goal for a bone: For example, a constant Y rotation, with a Z rotation axis saved as a separate action?

Here are details: I have created a swim cycle, deflecting a tail along the Y axis of three bones:

I would like to be able to add a flutter on another axis -- say Z -- and have that action smoothly intersect with the underlying cycle whenever and wherever it is used. Here is a Z wiggle:

In fact, I would like to do that with a flutter on the primary (Y) axis, too:

What I get, however, is the situation where the flutter action -- placed higher than the tail cycle on the NLA editor -- works fine, but ends up leaving the tail cycle deformed by the last position of the flutter NLA event. In the image below, the Z flutter has left the tail kinked downward:

My hope was to create action clips that added special or non-repeating action to an underlying strip but ended the "new" action -- the flutter in my file -- with a smooth return to the position of the underlying strip -- my swim cycle... Sort of like "take this cyclical position and add 10 degrees Z rotation, then subtract the rotation until it blends into wherever the underlying action strip is.."

So, that, with a question mark after it, is my question. How to achieve?

Answer 1

To be able to 'ease out' of an action strip that's higher up the stack and back onto a lower strip's:

1. Ensure the higher strip's Extrapolation values (found in the properties bar) are set to Nothing.
2. Play with the Blend out fields (also in properties bar) to phase out of the Action strip's influence. You can get a visual sense of how much easing is occurring by looking at the descending slope on the right part of the action strip (circled in picture).