The topic of musical similarity has surfaced again. British pop star, Sam Smith (who took home 4 Grammy awards) just settled a case (out-of-court) with Tom Petty and Jeff Lynne. Petty and Lynne co-wrote I Won't Back Down back in the late 80's. Sam Smith and 2 other songwriters (James Napier, William Phillips) co-wrote Stay With Me in 2013. Stay With Me has become a huge hit, and Tom Petty's people came to Smith's people to argue the new song borrowed too heavily from their guy's old song. The agreement that was struck: Petty and Lynne are now legally co-writers of Stay With Me. They will receive a percentage of the writing profits that previously went to Smith, Napier, and Phillips.
This is crazy stuff. There are only a handful of notes and chords available to pop/rock songwriters. Statistically, there will be phrases that resemble phrases from other songs. It's not done intentionally. It's simply impossible for it not to happen.
The notion of a writer and publisher owning a short musical phrase is ridiculous. [When someone pointed out to Brahms that a section of his First Symphony resembled a phrase by Beethoven, he snarled: 'Any ass can see that.'] But, if several measures are virtually identical melodically, rhythmically and harmonically (see: Lady Antebellum's Need You Now vs. Alan Parsons' Eye in the Sky) then, yes, the lawyers should start sending the scary emails. But, going after writers for 3 notes or 3 chords is overreaching and...