Replacing logic board on Nano 6th gen to retain music library.

If I understand you correctly you want to take your current working logic board that has your music saved on it and install it in another iPod. If this is indeed what you're trying to accomplish I would say that as long as the two devices are the exact same model you should have no problem swapping logic boards. But if the devices are not the same exact model then there will more than likely be compatibility issues. Identical devices should be using the same firmware and hardware which should allow the logic boards to be swapped without any issues but if the two devices are using different firmware or hardware the swap will likely not work. So as long as you are sure they're the same model you should be able to do this without any issues and be able to access your music library. If the music library is saved on SD card then you should have no problems. Hope I was able to help and best of luck with your swap.