This is where it all began. In the early days of heavy rock, three bands took loud electric blues as their starting point and then went in three rather different directions. Black Sabbath took the "dark path" and arguably invented the grungy, occult obsessed side of metal. Led Zeppelin transcended the blues and became the fab four of the genre, inventing stoner rock. Deep Purple on the other hand were the jazzier bunch. They were the better musicians and this album proves it. Lord was formally trained, Paice had more swing than Bonham and Gillan was a more versatile vocalist than Plant. The interplay between the band members on "In Rock" is ferocious and their dexterity is outstanding. This album serves as a great reminder of just how talented a guitarist Ritchie Blackmore is (was?). His fret speed is a direct precursor to Van Halen's blistering finger work, and influenced many of the great rock guitarists that emerged in the 70's. This album deserves recognition for the way its stunning power, volume and energy completely blew away practically anything people had heard at the time, and perhaps even more so for the fact that you can play it to modern metal/hard rock fans and they will often be still be blown away by the same qualities.