Opt in and opt out sounds like music to go in and out of ad breaks. I thought the Big Brother theme, though essentially the same had ever so slight differences every year. This year it's a (rather poor) digital feedback effect at the end of every sting.
Thanks Andy – I'm really tempted because it has the drum and bass only version of the underscore which I have been after for years! – They always use it when the ex housemates go back on to the stage on the final. Thanks for telling me about opt in and out!