Yeah, I understand how to mix Actions. For example if I have walking ad waving Actions, I can mix them into one Action - Walking and Waving at the same time. That’s not what I need.
Think about it as if you have an Action with walking anim. Then you want to add saddle movement to the character’s shoulders. Secondary motion in other words. The way I think of it is you would only tweak shoulder bones, and store new “corrective” keys only for those bones in a new Action. NLA would still mix those 2 Actions, but you only tweak keys in the secondary motion layer only for shoulder bones to adjust secondary motion. Those keys would add in runtime to the core animation action. Once you achieve desired result, you could bake core animation for whole body and secondary motions for shoulders into one final Action.
Can Blender do that? I can’t find any info about it. All tutorials for NLA and docs only talk about 2 different Actions mixing (like walk and wave, etc.) where each Action has different bones animated.
I recall 3DS MAX CAT could do corrective animation keys for existing animation keys.
In other words, if you think of it as 2 layers, the core animation Action (complete walk cycle for example) would be in the bottom layer, and shoulders secondary motion animation Action with keys only for shoulder bones is in the top layer (note that shoulder bones in the bottom layer would have keys set for shoulder bones, and keys from shoulder bones from the top layer would be added/blended to the keys of the shoulder bones from the bottom layer)
Am I making any sense?