The "Flavia" theme (which I guess is going to be a lot more common as a name, now the the Doctor has a new, exclusive personal theme) is this one. It plays after the Doctor walks away from Rose, rather than during the speech, but it's probably what you're thinking of.
The producers apparently thought it sounded like Flavia, and the name stuck. Looks like the last time we'll ever hear it is the start of Ten's regeneration.
ETA: That's weird. Half the post vanished when I edited it. Doubly so, because I checked it after I edited it, and it was fine. Maybe I used the back button when I shouldn't have. Anywho, I've recreated it.