Guitar World has an article on Yngwie Malmsteen’s 80s cover of the Highway Star which contains an undated quote from Blackmore about the two solos on the track, both becoming legendary:
I wrote that out note for note about a week before we recorded it. And that is one of the only times I have ever done that. I wanted it to sound like someone driving in a fast car, for it to be one of those songs you would listen to while speeding. And I wanted a very definite Bach sound, which is why I wrote it out—and why I played those very rigid arpeggios across that very familiar Bach progression — Dm, Gm, Cmaj, Amaj. I believe that I was the first person to do that so obviously on the guitar, and I believe that that’s why it stood out and why people have enjoyed it so much.
Jon Lord worked his part out to mine. Initially, I was going to play my solo over the chords he had planned out. But I couldn’t get off on them, so I made up my own chords and we left the spot for him to write a melody. The keyboard solo is quite a bit more difficult than mine because of all those 16th notes.
Thanks to Andrey Gusenkov for the info.