"Traditionally, jazz and opera had singers who were technically great singers, whereas in rock you had singers. But if they were a little sharp or a little flat, but no one really cared because they weren't expected to be perfect," he said. "As pop music becomes more artificially perfect, kids who grew up on that aesthetic want that perfection. When you're used to everything being on pitch, you don't want to hear anything else."
As a result, stars like Spears often perform with backup tracks to ensure they sound as perky and on pitch on stage as they do on their albums, after producers spend hours fine-tuning their voices.
Spears' November 2008 performance of "Womanizer" on the U.K. TV show "The X Factor" was panned by critics because she reportedly lip-synced although "X Factor" judge Simon Cowell didn't seem to mind. The "American Idol" mainstay gave the rebounding pop icon a standing ovation after her gig.
Levine thinks fans should stop expecting everything from Spears and her ilk.
"No one is going to go see Britney because she's a great musician," he said. "She's a good singer, but she's a personality. She's a phenomenon. She's not an artist, she's a pop star.".
But Tyler argued that Spears could up the ante, saying her "dancing is pretty physical but it's not so grueling that she shouldn't be able to sing as well."