I have given this five stars - but let me be clear and say that really there's no way to measure the "music" on this one. In fact, argument could be made that it's not "music" at all, but rather a wall of sounds like the echoes of an industrial revolution.
I wouldn't ordinarily even bother to comment, but when I looked this up on Amazon no-one had left a review, and that's a pity because - some time one day in the dim distant future - someone might stumble upon this listing and wonder: "What's that like?"
And the fact is, it's not like ANYTHING. While Klaus Schulze and Tangerine Dream were also making some rather radical Krautrock around this time, only Cluster it seems went for something that was totally beyond the boundaries of what constituted "music". This album is, basically, combination of sounds, rather than notes. It's all quite mechanical, noisy, and metallic. Machines groan, moan, and shudder. The structure is to have no structure, but don't confuse this with improvisation that bends the rules of the styles it's based upon, or stretches the instruments. This one breaks all the rules, and a kitchen sideboard can serve as an instrument.
I'm not sure what else to say. Tangerine Dream's Electronic Meditation won't prepare you for this. Klaus Schulze' Irrlicht won't. Stockhausen's experiments won't. The closest I could name - though it does it scant justice - is Lou Reed's Metal Machine Music. Though this (Cluster 71) is much much better.
Will you like this? Well, I don't mind saying I do. So if you're in a really adventurous mood, you might too. if nothing else you can ue it to convince your friends that you really have gone mad.