With pop stars like Britney Spears, it's all but expected that lip-syncing will go hand in hand with a live performance. Levine called it an open secret in the music industry, the product of audiences expecting artists to sound the same on albums and onstage.
"Traditionally, jazz and opera had singers who were technically great singers, whereas in rock you had singers," Levine said. "But if they were a little sharp or a little flat, t no one really cared because they weren't expected to be perfect. 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 onstage 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 believes 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 telltale 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," Levine said. "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**k off. Since when has lip-syncing been live? Anyone who lip-syncs in public onstage when you pay [about $169 per ticket] to see them should be shot."
Liz Rosenberg, the Material Girl's publicist, shot back, "Madonna does not lip-sync, nor does she spend her time trashing other artists. She sang every note of her Re-Invention tour live and is not ashamed that she was paid well for her hard work."
The debate didn't stop there. In an attempt to help out his pop star friend, actor Rupert Everett added fuel to the fire, telling the British media, "Madonna sings everything she can sing. ... But, if she goes into a dance routine, she's got to dance. You can't breathe and dance and sing at the same time."
Some stars couldn't cry libel or count on their celeb friends for defense when it comes to lip-syncing accusations.