Deep Purple in Rock

The album was made between October 1969 and spring 1970 at three London studios, in the gaps between gigs. Andy Knight engineered the IBC sessions, which gave Speed King, Child in Time, Into the Fire and Living Wreck. Martin Birch engineered at De Lane Lea and became the band's regular engineer through 1976, and the original sleeve credited him as catalyst. Phillip McDonald engineered Bloodsucker at Abbey Road.

The band had rehearsed at Hanwell Community Centre from the summer of 1969, and Child in Time and Speed King, then called Kneel and Pray, were in the live set by the seventh gig, in Amsterdam on 24 August 1969. The title was a reaction to the Concerto for Group and Orchestra, and management designed the cover, which puts the band's faces on Mount Rushmore. Speed King opens with an instrumental piece called Woffle, which the US pressing cut. Blackmore said he wanted to have a go at being really heavy after hearing Led Zeppelin's debut.

It reached number four in Britain and stayed in the charts for over a year, though in the United States it peaked at 143. It was number one in Germany. Record Mirror called it a stunningly good album in 1970, and AllMusic's Eduardo Rivadavia later described it as one of heavy metal's defining albums. Blackmore has named it, with Machine Head, as his favourite. The single Black Night, which was not on the original LP, was added to the 1995 anniversary reissue.

Sid Smith of the BBC wrote in 2007 that the album pretty much carved out the template for heavy rock. He heard Into the Fire as drawing on Hendrix and Cream, and noted that Child in Time was adapted from Bombay Calling by It's a Beautiful Day. Speed King was the first Deep Purple song written by Gillan. It grew from a bass riff by Glover that was meant to echo Hendrix's Fire, and Gillan assembled the lyrics from lines of Elvis Presley, Little Richard and Chuck Berry songs. In Britain it was the B-side of Black Night.