My laptop suddenly and for no apparent reason started playing techno music. I started digging around, closing app and browser window after window until it finally stopped. Turned out to be coming from google reader. I re-opened reader and the music came back. I went thru and marked a bunch of items as read, closed it, re-opened again, and it was gone.
So the source was some post being viewed in reader, but it’s not obvious which post it was. It wasn’t the one I was currently reading; I think reader keeps some number of posts in its buffer so you can go back and forth.
Anyway, interesting behavior. I wonder if reader does anything to sandbox posts from each other? I hadn’t thought about annoyance/attack by RSS before, but I guess it renders to browser so it’s possible.