"The chords are one-four-five," Campbell tells Billboard. "Those are the blues. You don’t get more basic than that. I think what’s more reminiscent of the Leppard thing is the production, the sound, the vocals, the reverb and the way it’s asssembled.
"That is very flattering that all of a sudden these kids think it’s a cool sound. I think a lot of people of their generation aren’t going to connect their music to ours."
The songs aren't totally dissimilar. "Midnight Memories," which peaked at No. 12 in a one-week run on the Hot 100, subscribes to the same arena rock standards on which Def Leppard made a name, particularly with "Sugar." The chorus especially is a guitar-laden stomp, with vocals meant to be belted at the top of one's lungs.
But this isn't a matter like, say, Robin Thicke's "Blurred Lines" vs. Marvin Gaye's "Got to Give It Up," according to Collen.
"That’s different," he says. "In fact it’s got the mayonnaise jar and people hooting in the background which Marvin Gaye had. I don’t see that you can do that. The One Direction one is very similar in structure, but it’s all good."
Interestingly, it isn't the first time One Direction has been pegged by naysayers as ripping off a classic rock act on its new album. As Time reports, the boyband was accused of lifting key elements of The Who's "Baba O'Riley" on lead "Midnight Memories" single "Best Song Ever."
But as with Def Leppard, Who frontman Pete Townsend wouldn't have any talk of legal action, noting in a statement in August that "the chords I used and the chords they used are the same three chords we’ve all been using in basic pop music since Buddy Holly, Eddie Cochran and Chuck Berry made it clear that fancy chords don’t mean great music -- not always."
Billboard reached out to One Direction's camp, but a request for comment was not returned.
"Midnight Memories" debuted at No. 1 on the Billboard 200 upon its release, selling 546,000 copies in its first week according to Nielsen SoundScan.
Additional reporting by Marc Schneider and Andrew Hampp