This is the first incarnation of Deep Purple, colloquially known as Mark I (they had several incarnations of the band. I’m a fan of the first two). About half of the album is cover material as the band didn’t feel like they had enough original material (Link https://www.vintageguitar.com/2822/ritchie-blackmore/).
Ritchie Blackmore played a Gibson ES-335 guitar in this incarnation of the band, and switched to a Fender Stratocaster in the Mark II version of the band, beginning with the “In Rock” album. If you are familiar with the recordings of both early versions of Deep Purple, I’m sure you can tell the difference in guitars.
Both Blackmore & Jon Lord (Hammond organ) drove their instruments through Marshall amps to give them great, thunderous sound. Lord chose to do that in order to maintain sound equality with Blackmore’s guitar as can be heard on the record.
I feel most folks are more familiar with the Mark II version of the band given the commercial success of this incarnation (“Smoke on the Water”, “Highway Star”, “Speed King” and “Woman from Tokyo”). So this is a little shout out to Mark I, a hint of the greatness that was to come, yet a good sound all their own – more prog rock & airy than heavy metal, a direction that Rod Evans (lead singer Mark I) expanded on in his next band, Captain Beyond.
And, for you fans of Mark II, here is Deep Purple “Made in Japan”, arguably one of the best live albums made.