Even those who do not follow the intergalactic and time-travelling of the Doctor would probably recognise this distinctive theme music with its eerie electronic bubbles and hisses and hypnotic quality.

Remarkably, it was conceived long before present-day electronic music techniques were available. The original tune was written by the Australian composer Ron Grainer (1922-1981) but the version we are familiar with was largely created in the famous BBC Radiophonic Workshop by Delia Derbyshire (1937-2001). She appears to have been an indomitable personality as well as a talented one. She came from a relatively humble background, but learning was valued in her family, and it is reported that she taught other children to read when she was only four years old. But the love of her life was the radio, and she also proved very musical. Somewhat less than helpfully, her careers advisers suggested she might consider a career-making hearing aids.

After a spell working for the UN in Geneva (and helping her finances by giving piano lessons) she was taken on by the pioneering BBC Radiophonic Workshop. To his infinite credit, Grainer was desperate for her invaluable contribution to be acknowledged - but she was not given an on-screen credit until the show's 50th-anniversary special.

More Info: en.wikipedia.org