"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 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."
Unlike Spears, Madonna's routine on her Sticky & Sweet world jaunt and on tours past is more suited to marathon runners than musicians. The 50-year-old queen of pop performs high kicks and running jumps as she bounds across stage, yet never seems to struggle for breath. It's a tell-tale sign she's probably performing with a backup voice track.
"If you look at the way pop stars perform, the way they're twirling, running, being carried, dancing on the stripper pole upside down -- they can't possibly be singing every word of every verse," said Levine. "A lot of times it's blended, they might be singing with a safety net. Any pop singer putting on a full dancing show is not singing every word in those songs. The fact that they're not breathing hard should be enough to clue you in."
At London's annual Q Awards show in 2004, Elton John bashed the pop star for not performing up to par on her Re-Invention tour, saying "Madonna, best f-- live act? F-- off. Since when has lip-syncing been live? Anyone who lip-syncs in public on stage when you pay [about $169 per ticket] to see them should be shot."
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