Change all bones of an already existing animation I am a noob in Blender so I hope this question is not extremely trivial. I want to modify an existing animation. The animation is made of a lot of frames. The position of the rig is mostly fine, a part from (let's say) the head. I want the head to be slightly curved on one side, for all the frames.

Now, I can see how to do it for a single frame (through the graph editor, for example, or by moving the model and pressing I). But what if I want to do it for a bunch of frames? Is there a way to doing that fast? 

Thanks
You can do all basic manipulations in graph editor same as with objects in 3D-View, like scale, translate and rotate, border select, select linked and more.
Just select the keyframes that you wish to change and move them all by one by pressing g. Press y to lock moving only the values and not along the time axis.