"One of Deep Purple's four indispensable albums (the others being In Rock, Machine Head, and Burn), 1971's Fireball saw the band broadening out from the no-holds-barred hard rock direction of the previous year's cacophonous In Rock ... Sure, the following year's Machine Head would provide Deep Purple with their commercial peak, but on Fireball, the formidable quintet was already firing on all cylinders"