Can Songcast keep running when another user logs in?

I've finally started using Spotify. Started off with streaming from the iPad, but now using Songcast on a Mac. It works well, but I'd like to be able to lock my account and leave the music running (and let other users log in) without interrupting playback.
Is that possible?
If not, would it be possible on the PC?
Thanks in advance!
Loz