Evidently someone discovered the similarities and Tom Petty & Jeff Lynne were added as co-writers of the Sam Smith song and will receive a percentage of the song's income. Nobody says that Sam Smith copied the line or stole anything but the other two are still receiving royalties because they own that six note phrase.
Here's the problem... as long as one stays with a single key, there are only a limited number of notes that can be placed in a limited number of orders. Add the way that western music works and the way that pop music works and things become even more constrained.
Here's another video mashup that shows this issue in a funny way.
and yet another one
Search for Pachabel's Canon rant on youtube for yet another....
Now, I'm a song writer and I believe that artists should own their work. I also have a BA in music. I remember a composition class where the prof made a statement that struck me as odd... and I expect an understatement. She said "every melody that could possibly be written was written by the 14th century." That is, every melody you ever heard was a copy of something written long, long ago. I am sure that if we looked a bit we could find another instance of those 6 notes in the Sam Smith/Tom Petty song. It is a great little line and it was not original to Tom Petty. If you're a songwriter, everything you have ever written has already been written by someone else. Here's the point though. That doesn't make you less of an artist. You still have taken those same six notes and given them new life, new meaning, and new emotional content.
So here's my rant... to own those six notes (which is what is being acknowledged here) is just ridiculous. I would say the same thing about DNA and any number of other examples of intellectual property. The laws need to be updated to reflect the reality of the situation.
For a bit of fun, Jon Stossel recently wrote a column on intellectual property. I think it is the first (and like the last) time I've agreed with him.
FWIW, I prefer what Sam Smith does with the 6 notes over what Tom Petty did.