In 1968 Lord helped form Deep Purple which was an amalgam of the hard rock at the time with classical undertones. The band along with Black Sabbath and Led Zeppelin are considered Heavy Metal's Founding fathers. In 1970 Deep Purple released 'Machine Head' and for the next 30 years (with a few breaks in between) Lord's keyboards dueled with Richie Blackmore's guitar. With all the lineup changes that plagued Deep Purple, Lord (until his retirement in 2002) along with drummer Ian Pace were the only constants.
In the longest break Deep Purple took (1976 - 1984), Lord played keyboards with former Purple vocalist David Coverdale in Whitesnake. Lord appeared and contributed to the first six albums and left to join the Deep Purple reunion following the release of their best disc 'Slide It In'!
To get the best sample of Jon Lord's talent and abilities, go no further than 1974's 'Burn'. One listen and you can hear where bands like Dream Theatre, Helloween and Yngwie Malmsteen's Rising Force get a lot of their influence!