Doctor Who's original 1960's intro is in a similar vein of "wait a minute, how'd they do that in that year?". This predated any commercial synthesisers and was mind blowing for its time.
https://www.youtube.com/watch?v=75V4ClJZME4
https://www.effectrode.com/knowledge-base/making-of-the-doct...
The theme is much more subtle and complex than my mental model.
I can recall in an electronics lab in university, we had just built the first prototype of input and output stages for an amplifier, and hooked it up to a function generator playing a sine wave and probably a simple paper-cone speaker. The system had fairly heavy hyperbolic distortion (as I expected from following along with the textbook)... my lab partner (who up until that point I'd thought of as not especially bright, relative to the standards of the course) listened a bit, grabbed the frequency knob, identified a few pitches, and then started playing the main melody of the Doctor Who theme entirely by ear. (And of course I provided a vocal bass line accompaniment, almost instinctively.)
The BBC Radiophonic Workshop was just incredibly innovative. I spent a long time learning about them and their techniques as a music student.
> Composed by Ron Grainer, realized by Delia Derbyshire of the BBC Radiophonic Workshop.