A few years ago, back around the time that Kanye West interrupted Taylor Swift, there was another bit of news in the music media. Coldplay had come out with a song, Joe Satriani heard it, and felt pretty devastated by what he heard.
The suit was eventually settled and dismissed. The rumors I've seen were that Satriani got a cash payment from Coldplay, but that's hard to confirm. Coldplay didn't admit wrongdoing.
But what was interesting about it was that the argument mostly centered on the chord progression! The chord progression in question was VI-VII-III-i , or IV-VII-III-i. (VI and IV are pretty similar and serve the same function due to common tones.)
That chord progression seems rather distinctive - a far cry from the cliché four chord songs everyone likes to joke about. Right?
Right?
Well... let's take another look. Both of those chords end up on the minor "one". And minor keys have relative major keys. What would those chord progressions be in the relative major? IV... V... I... vi. And, ii... V... I... vi. That's pretty much the "four chords" right there. The latter one is basically every jazz turnaround ever at the end of a standard. The only twist here is that they chose to label the chords in terms of the relative minor. And that's arguably wrong of them, anyway. Coldplay's song is in a major key the entire way through (not a V/vi to be found), whereas you could argue that Satriani is minor in the verse, and modulating to the major in the chorus before it goes back to the relative minor.
To me, the similarities are more convincing because of tempo, groove, and the key parts of the melody - the melodic rhythm in particular. I think that's where the strength of Satriani's claim was, supported by the chord progression - not in the chord progression itself.
However, I suspect that in trials such as those, they don't look at it in terms of each particular ingredient - they just play it for the jury and ask them if it sounds "too" similar. I'm also not surprised this lawsuit turned into a settlement, because if Coldplay had been found liable based off of a combination of factors, it would have opened them up to a ton more lawsuits from everyone else who happened to write four-chord songs that they believed sounded similar. (Which almost happened with Cat Stevens anyway, due to his ii-V-I-IV progression...)
