Well, evolving an artform is always a communal, societal effort. Just look at the key word there: Stop, collaborate, and listen.

That's how Ice was back with his brand new invention.

Well there's sampling and then's theres just reproducing a whole song.

You could steal a single riff from Metallica and they would be up in arms.

You don't have to steal a whole song to plagiarize it. It's plagiarizing to copy a single sentence without referencing it in a paper, why isn't music the same?

That's just it, it is.

Except for when it isn't.

It's not plagiarism if the artist had no idea they were the same. It's entirely possible that Coldplay simply didn't realize how similar the two songs were.

All artists that sample have to credit the song they sample and pay a fee or royalties...or get sued into oblivion (See KMFDM, re: The original 'Naive' album and Biz Markie, re: "I need a haircut")

And sampling or not, you're taking someone elses idea and making money off of it. Even if its only a small bit of it.

its possible and the chord progression doesn't really bother me but the melody does.

They are terribly similar.

It is the same, but this is more like using the same 2 or 3 words in a row that someone else used, and getting complaints from them even though lots of other people used that phrase before either of you, and it isn't a particularly creative phrase anyway. I didn't even mention plagiarism there; I was just contradicting this:

Edit: Again, yes, the melody is very similar in some places, but also extremely simple. Is it really so surprising that, out of the millions of pop songs made in the past few years, one of them ended up using the same 3-note riff, along with a similar background melody because it's one of the few background melodies (of such extreme simplicity) that goes well with that riff? Music isn't random; certain sounds go well together, but most don't.

The problem is that not only is the chord progression that the coldplay song seems based on nearly the same as the Satriani chorus, but added the fact that the tempo and meter are basically the same too, and it you can see where it looks like it may very well have been stolen. I am not saying it was, but there is certainly enough similarity that it warrants a look.

Except that's actually not what happened at all with the Amen Break. In fact it was sped up slightly and copyrighted by an entirely different entity than the original copyright holder, meaning it is owned by at least two different legal entities, one a company one a person.

Also, that was not always the case, nor should it be the case now (though it is).

Did you watch the video? Because you should.

Taking someone else's idea and making money/popularity/whatever else off of it is pretty much how our entire artistic culture evolved.