How exactly is a blend using a weight of 1 supposed to work?

I have a run cycle that has animation on the arms,

I also have an animation which is upper body only, if I blend this using a weight of 1, am I right in thinking the aim animation on the upper body should completely override the motion on the arms from the run cycle?

What I am finding is that I get odd results which looks like a halfway point between the two. Can anyone shed any light on the correct way to set this up? thank you.

you are using an ApplyAdditive node. if you don’t want additive blending, you should use a Blend node instead:

That causes some REALLY weird behaviour. Really what I need to know is - are my animations set up right for blending, hence the wording of the original question. In theory with what i’ve described, should blending with a weight of 1 give me the right behaviour? what are the pre-requisites for an animation you blend with?

do you want the animation to only affect the arms?
if you only want the animation to blend some of the bones, you should use a layeredblendperbone node:

thank you! I’ll give it a shot.