iTiR for Mac

From Hacking The Soul:

iTunes interuser-Remote (iTiR) was written to get around a problem with iTunes and Fast User Switching. When Fast User Switching is used, if one of the users has iTunes open, then the music is paused when that user is not the active user, and the other users can not launch their own copies of iTunes. This can be very frustrating if you are switching users often, but still want to listen to your music.
iTiR is made up of two applications. The "iTiRbase" application and the "iTiRremote" application. The iTiRbase MUST be running in the same user space as iTunes, and it acts sort of like an IR repeater for a TV. Basically, it captures the commands you give to iTiRremote, and passes them on to iTunes. iTiRremote is the interface that you use in all the other user spaces to control iTunes (or to quit iTunes so you can run your own copy).