I've owned this CD for quite some time now, I decided to take a look and read peoples reviews/comments - sadly I see no-one has gotten around to posting any.
Oh well then, I guess it's up to me.....
I particularly enjoy avant-garde/experimental music. As such, this album isn't remotely scary. For fans of pure classical music, or for folk who enjoy pop/rock, then there are a few challenges here. For a start there isn't a trace of melody to be had, and secondly the treated pianos and very basic electronic equipment throw up odd squeaks, plonks, and strangely vibrato "notes".
What it is, however, is endlesly fascinating. There simply isn't time to get bored as the shape, structure, and density of the music wavers, comes and goes, flowing and splashing about. If that sounds messy, well I guess it is. But mess can be fun (if nothing else, it's fun to make!)
I think that sense of fun can often get lost on experimental pieces like this. Most of the time the artists are so darn serious the playful naughtiness gets lost. Which is a pity. Sure this is music you can sit and examine, but at the same time it's so odd at times that it equally fascinating to allow yourself to be amused.
What other thing is it like? Wow. With the prepared pianos you can't get away from John Cage. On the electronics front I struggle to find something similar. You're more in the world of Cluster (Krautrock) than anything else. Most people forget thre Vangelis album on Deutche Gramaphon called "Invisible Connections", but that is a purified version of this in many ways (the Vangelis album is really worth checking out for adventurous minds, it's NOTHING like the usual Vangelis music).
Anyway, Kontakte is a great piece of music. Yes, it's for those who tastes essentially have no bounds, and yes it'll no doubt annoy some looking for more conventional thrills. But this is Stockhausen we're talking about, so no excuses ought to be necessary.