It is a guess on my part but I think your MPK is on the same midi channel as your APC.
I have no experience with it (the MPK 25 is still on my wish list
) but I do notice that the controls seem match those somewhat of my MPD. So here goes; if this doesn't work you really should check your manual or reference guide on how to do this.
My suggestion is to set your MPK to midi channel 2 so that it doesn't overlap with the APC.
My guess on how to do this:
- Press 'global' (under your lcd display).
- Press "move right" (under the jog/enter dial, to the right of your lcd).
- Now eventually something like "Channel 1A" might appear.
- Now use the jog/enter dial and click one clock wise to turn this into 2A.
- Now continue pressing "move right" until it says "save setup".
- Click enter (push the jog/enter dial).
Keep in mind: do this when Live isn't active, and start Live after finishing this task.
Now if all went well you shouldn't have these issues anymore.
If something on your MPK doesn't match my guessed points don't continue but check your reference guide on how to change the midi channel.