A lot had changed for Deep Purple since the beginning of 1970, the year In Rock was released. Their label, Tetragrammaton, had gone bankrupt, and the group had moved to Warner Brothers. Changes in band members found the classic Deep Purple Mark II line-up of vocalist Ian Gillan, guitarist Ritchie Blackmore, keyboardist Jon Lord, bassist Roger Glover, and drummer Ian Paice in place. Gone also were the cover songs and orchestration of their earlier releases. Deep Purple was now poised to help create a new brand of rock & roll known as hard rock, which would ultimately become heavy metal. Meanwhile, Led Zeppelin and Black Sabbath were achieving massive sales and changing the face of modern music.
Though In Rock did not sell well in the 
What set Deep Purple apart from their contemporaries was the speed of many of their songs, plus the dual organ-guitar blitz which provided the foundation for their sound.
“Speed King” leads off the album with a blast of frenetic fury. Ian Gillian shrieks, “I’m a speed king, see me fly” as Blackmore and Lord duel on guitar and organ. Blackmore’s guitar playing established his and Purple’s sound with this very first song, and it remains a staple of the group’s live act (and is still played at hyper speed.)
“Bloodsucker” is very much a Ritchie Blackmore song. Ian Gillan provides a competent vocal, but it is Blackmore’s continuing quest to establish himself as a force in rock music that drives the song. This track looks ahead to Blackmore’s later group Rainbow.
Side one of the original album release ends with the classic “Child In Time.” This ten minute tour-de-force remains a Deep Purple signature song. It’s particularly nice to hear a more mellow vocal style by Gillan. The instrumental sound runs counter to the harmony as Blackmore and Lord take the sound in an almost a neo-classical direction.
The second half of In Rock is not as strong as the first. “Into The Fire” and “Living Wreck” both have odd structures, and Blackmore and Gillan give only fair performances. “Flight Of The Rat” is better as it returns the group to a frenetic mode and allows Jon Lord some room for improvisation. “Hard Lovin’ Man” ends the album on an average note, almost as if the group has expended its energy.
In Rock would set the table for a long career on the part of Deep Purple. Two classic songs and two more very good ones allow this album to remain a pleasurable listening experience -- and don’t forget to turn it up loud.