After completing the recordings at the end of 1971, Deep Purple released Machine Head on March 25, 1972. The band's sixth LP immediately shot to No. 1 in the UK and stayed in the charts for weeks, also thanks to the singles "Never Before", "Lazy" and "Highway Star". Machine Head was a slow success in the United States, partly because "Smoke on the Water" was not released as a single until May 1973. The song became Purple's most successful US single (which reached #4 on Billboard, as did "Hush" from 1968) and pushed his mother album to #7. Overall, Machine Head spent more than two years in the American charts, while Deep Purple became world-famous hard rock heavyweights. Decades later, it is still the band's biggest album.