I transfered IPad from PC to Mac...de-authorized and signed in...found ITunes has both my music and music from the previous ITunes account even though it was also de-authorized and signed out and a new sign in ITunes account....

My wife and I decided to switch PC's. She had an Mac Pro and I had a PC. Both of us have Itunes (Ipad, Iphones). She moved her ITunes library to a new PC and de-authorized and signed out from her old Mac Pro. She signed in and authorized her new PC. I took her Mac Pro and followed the same process. In the end we both found our ITunes library mix in with each others music and books. Despite the fact we are both signed in to our own ITunes account. Seems like the devices (IPad, etc.) stays linked to the original computer....these devicdes did not contain mix Itunes library (eve after they were synced).