The original TV broadcast used synthetic samples, while the soundtrack release features a re-recorded version with a full orchestra . If you'd like, I can: Find sheet music or piano tutorials for this track
Compare this theme to the of other Doctors (like "Vale Decem" or "The Shepherd's Boy") Few examples of returning themes in Doctor Who music
Music editors found the track so effective that they repurposed it for the climax of the regeneration itself.