This theme is not techno, which is something I always associated with the Doctor, and so amazing. It is a heartbreaking theme for the last Billie Tyler appearance. Although Rose and the Tenth Doctor had a romantic relationship, this theme could have been applied to other intense relationships that had been ended, such as the death of a child. You definitely do not have to have seen the episode to know that the parting was not voluntary. Another great Doctor Who track, beyond the theme, is 'Bad Wolf Theme'.