666 and aphrodites child

Possibly one of the most unlikely pairings in progressive rock produced an even more unlikely classic -

"Aphrodite's Child was a Greek progressive rock band formed in 1967, by Vangelis Papathanassiou (keyboards), Demis Roussos (bass guitar and vocals), Loukas Sideras (drums and vocals), and Anargyros "Silver" Koulouris (guitar).
The band began to record their crowning achievement late in 1970: a musical adaptation of the biblical Book of Revelation, entitled 666. Silver Koulouris, having finished his Greek army duty rejoined the band. However, relations between all the band members were not good at the time, and continued to worsen during the album's creation."

And while we're all shuddering over the idea of pop schmooz Denis Roussos singing prog rock this "genuine mind blowing" double album was the concept of Vangelis.

"By the time the double LP 666 finally came out in early 1972, and having sold over 20 million albums, the band had already split. Both Vangelis and Demis Roussos pursued successful solo careers, Roussos as a pop singer and Vangelis in electronic music. Koulouris worked with both on occasion. Loukas Sideras pursued a less successful solo career, releasing an album and the single "Rising Sun" after the break-up."
wiki article

Reissued on cd and 180gram vinyl by Universal Music on their Back To Black catalogue. Presented as exact reproductions of original LP artwork to retain authenticity. Which in the case of 666 is not a revelation.
Amazon and other outlets will have the full details.
And if you don't know this album... prepared to be amazed. Here's the track "The Four Horseman".