On the other side of this coin, I have Sirius Deep Tracks on at home, and they are playing Taurus by Spirit, though I didn't know it at first. I definitely hear the part they're talking about. I actually thought I was hearing some alternate acoustic version of Stairway for a few seconds.
I looked into this a little more. Every time the song is distributed, it's considered a renewal of the violation (or something like that). So if this occurred within the "statute of limitation" period going backward from this point in time, then a claim can still be made. Not at first... only after threat of lawsuit from Berry and/or his publisher. Kor
The whole "Stairway"/"Taurus" thing is nowhere near as egregious as some of Zeppelin's thefts, such as putting their name to the entire song (music and lyrics) of Moby Grape's "Never" and retitling it "Since I've Been Loving You".
In case anyone hasn't heard, the case is over, the verdict returned and Led Zepplin was found NOT to have infringed the copyright. http://www.abc.net.au/news/2016-06-...-of-stealing-stairway-to-heaven-intro/7539542
I wonder if part of the defense was that Randy never made any claims of plagiarism in all the years he was alive.
I've heard it explained that the chord progression is common enough. An example was used comparing the Taurus song and Stairway to Mary Poppin's Chim Chim Cher-ee. As crazy as that comparison sounds, I could actually see their point.
...and Dido's Lament by Purcell, apparently, is another example of a descending chromatic minor line progression. I don't hear the similarity myself but then I'm tone deaf.