Over the last couple of weeks, the sounds of pop's biggest hits have been distractingly familiar. Almost as soon as it hit the Internet, "Roar," the brand new smash by Katy Perry, was accused of sounding an awful lot like the recent song "Brave," by Sara Bareilles. A legal dispute now surrounds the No. 1 song in the country, Robin Thicke's "Blurred Lines," over its similarity to "Got to Give It Up," the 1977 hit by Marvin Gaye.Today on All Things Considered, NPR's Neda Ulaby talks with NPR Music pop critic Ann Powers about the history of pop sound-alikes. "Songwriters have borrowed from each other, played off each other. People have claimed the right to songs in the public domain," Ann says. "This is part of the art of pop."