For a while now, classical music has filled the small ground level part of Kentish Town tube station in the evenings. Maybe it's more than just the evenings but that's when I tend to notice it.
I imagine this is intended to be calming to the frustrated and weary traveller, perhaps reducing the amount of aggro the staff get. I've heard of similar schemes used elsewhere. If nothing else I imagine it keeps the staff amused seeing as they have to stand in that small hall all day. Personally I only wish they'd turn the volume up!