I just bought a new CD of Deep Purple's "Fireball," which is a great album!
The song "The Mule" always impressed me as possibly being inspired by Isaac Asimov's famous "Foundation Trilogy," which I was reading at the time the LP came out (1970).
Searching around, I found that Ian Gillian confirmed what I had guessed forty years ago!
"I'd like to ask you about the lyrics to 'The Mule'. Am I right that it is based on one of
my favourite novels, Foundation by Isaac Asimov? Was it written by you, and if yes did you read the book?"
Nothing but the best,
Tamás"
"Hello Tamas,
Thanks for your letter, comments and questions. Yes, The Mule was inspired by Asimov. It's been a while but I'm sure you've made the right connection...Asimov was required reading in the 60's."
(The Mule was a mutant bad-guy in "Foundation," named The Mule because he was sterile.)