The first two Deep Purple albums featuring the Mark I line-up were far from bad. With their blend of psychedelic, progressive, and hard rock, they showcased the virtuosity of Blackmore and Lord, offering a highly distinctive sound right from the start. The classic Mark II line-up — Ritchie Blackmore, Ian Gillan, Roger Glover, Jon Lord and Ian Paice — made its debut with "Concerto for Group and Orchestra" and once again expanded the band's sound, partly thanks to the charismatic Ian Gillan on vocals and partly because the band were now confident enough to leave the boundaries of the genre behind. It is perhaps therefore not so surprising that the Mark II line-up's debut studio album, "Deep Purple in Rock", virtually defined and revolutionised the hard rock genre. From then on, this album (and the subsequent Mark II albums) became synonymous with hard rock. At the same time, with their solo escapades, Blackmore and Lord took their musical rivalry to absurd heights, adding influences from classical music and progressive rock to ‘pure’ hard rock with their virtuosity. The result remains stunning: "Deep Purple in Rock" is a (pun intended) rock music classic set in rocks err stone.