How to increase frequency of a repetive animated movement? following setup: Blender 2.79 freshly downloaded from builder.blender.org
on Linux (GENTOO) using Cycles.

In a animation I have a character using a saw to cut wood. In a fast movement
the character pushes the the saw away from him/herself and then pull it more
slowing to him/herself.

I animated one movement manually
So far so nice.

One push/pull will not cause anything serious.... ;)

Now the problem:
a) This push/pull movement should be repeated many times.
b) The movement should become faster and faster.
c) I dont want to animate every single push/pull manually.
( d) I got headaches while searching for a neat solution.)

Repeating a movement is not that problem. But anymating the flow
of time over THE WHOLE THING is a problem for me.

How can I acchieve this?
Found a possible solution myself.
Steps to perform:


Animate one motion manually. This motion will be repeated and speed
up in later steps.
For the NLA strip created that way set the count of repeats in the
N-key panel.
In the timeline set the start and end to the first frame and to the
last frame of the NLA-strip including all repetition.
Deselect all strips in the NLA editor.
Only Select the NLA strip in question.
Now bake the animation. I choose "object" to be baked. This can take
quite some time.
The result is an additional strip, which includes the complete
animation as it had been animated by hand frame by frame.
Now it is possible to animate the flow of time of this newly created
strip easily.
Disable the the original strip (the one with the repetition modifier
set). You can use this as an backup for later modifications.
Play the animation.


This is one possible solution, which leads to what I wanted. I am sure, there will be other options to fine tune the result and especially speed up the baking time.