"It was at one point the longest album ever released as a single LP, but it was overtaken by Def Leppard's Hysteria album in 1987. Being a 60+ minute vinyl LP, Warner Brothers Records used Noise Reduction, which lowered the volume considerably, on all tracks to fit both sides equally." (quote from: https://en.wikipedia.org/wiki/Deepest_Purple:_The_Very_Best_of_Deep_Purple). It's really noticeable. The guitars sounds at least good but the problem is with Lord's organs. One really need to turn up the volume to hear them (most notably on Fireball and Speed King solos). Expected a better sound. My copy sounds a bit better on side 2 though. Good side - the tracks are studio cuts. Bad - this doesn't sound that good as it should. Or it could be just my copy's fault which is in worse state than other Japanese LPs I have.Edit (28-29.05.2018) - Sounds much better than previous time! Probably it needed a test spin in order to get the dirt and stuff out of the grooves. Actually, it's a Fireball !