TV's singing competitions have become star wars.
On NBC's The Voice, which opens Season 3 tonight (8 ET/PT), Christina Aguilera leads an all-star panel of coaches. Fox's The X Factor, which returns for its second season Wednesday (8 ET/PT), has retooled, adding Britney Spears and Demi Lovato as judges.
And Fox's American Idol will come back in January with pop diva Mariah Carey (once courted by X Factor) and probably other marquee names.
The on-screen arms race doesn't even count the bounty of performers, from Rihanna (X Factor) to Katy Perry (Idol), who have made guest appearances. This season's Voice mentors include Billie Joe Armstrong, Mary J. Blige, Michael Bublé and Rob Thomas.
It's a far cry from the genre's beginning 10 years ago in the USA, when Idol premiered with a judging panel that featured a British recording executive (Simon Cowell), a pop singer whose chart-topping days were well behind her (Paula Abdul) and a music producer (Randy Jackson).
Both The Voice and X Factor have star-driven lineups for their fall faceoff, but there are differences. The Voice, which avoids harsh critiques, features an established group composed entirely of performers (Aguilera, Cee Lo Green, Adam Levine and Blake Shelton), while X Factor, which won't hesitate to criticize poor talent, balances newcomers Spears and Lovato with returning pro talent evaluators Cowell and L.A. Reid.
But could the search for new talent dim beside the glow of ever-hotter celebritydom? "On the current crop, it seems to me that the judges are getting more out of it than the contestants," says Cowell, executive producer of X Factor.
"What works on X Factor is that you do have two very, very good record executives sitting on either side of the talent," Cowell says. The genre has "morphed into who can hire the best-known celebrity, but it will only work if these celebrities know how to spot talent."
Voice executive producer Mark Burnett says that he was looking for young, relatable stars and that their mix has been one of the appeals of the show.
"I had no idea about the chemistry, (but) I did know I wanted the coaches to be cool and to appeal to young America," he says. "Christina had a huge, long career, and I really wanted Christina. In terms of the guys, I'd been fans of them all and thought it would be a great opportunity for them to work on the show and rise together. And I think (they) did. It was really mutually beneficial for everybody."
Star judges bring a level of expertise and showmanship, says Trish Kinane, president of entertainment programming for Fremantle Media North America and executive producer of X Factor, Idol and NBC's America's Got Talent. (Talent caused a stir this year when it brought in Howard Stern as a judge.)
"Judges need to be able to perform in an entertainment program. ... That's probably why we've ended up with celebrity judges," she says. "They have the expertise in what the song should sound like or how good the voice is, but they also have lived through the late nights (and) grueling rehearsals."
Shining stars also attract media attention, which can help generate buzz in a crowded genre that this year has also featured AGT, Dancing With the Stars and Duets. The conversation about Nicki Minaj and Keith Urban being considered for judging spots on Idol provides plenty of preseason promotion.
"It's become this kind of stunt-casting thing that seems like it has escalated out of control," says Richard Rushfield, author of American Idol: The Untold Story. "When they started (these shows), Idol had one seat for a star, pretty much a retired star at that. Now, it's like all the seats have to be filled by stars - and stars that are more tabloid-driven stars than necessarily great singers or great hitmakers.
"For me, the Steven Tyler-J. Lo path (on Idol) is the perfect cautionary tale. Initially, it gave Idol this huge burst of interest and made the ratings go up. But then the reality was they were not very compelling judges, and the second-season ratings plummeted."
Whether a star will provide commentary that engages viewers is hard to gauge, Atlanta Journal-Constitution blogger Rodney Ho says. "We thought Steven Tyler would be this wild-card, nutty judge, but he just became a very, very long thesaurus for the word 'beautiful.' "
Just a few years ago, current artists probably would have shunned reality shows as cheesy. Jennifer Lopez's decision in 2010 to join Idol, which reignited her career, may have persuaded others to consider such a move.
The Voice's Shelton can see benefits. "It's tripled my visibility, with people learning my name and possibly buying a record," he says. "It's definitely made a huge difference in my career."
Stars can reach a larger potential fan base, says X Factor's Lovato. "This is a show that's not just targeted to a young audience. It's people of all ages, and I'm very excited to get my music out there."
Despite multimillion-dollar paydays, don't expect today's stars to stick around as long as Cowell, Abdul and Jackson did. As The Voice moves to two cycles a year, Burnett says, coaches may take leaves for recording and touring, and Fox entertainment chairman Kevin Reilly says change could be more frequent on a long-running show like Idol.
Contestants should be the ones in the spotlight, Cowell says. He notes that Levine "has had two huge hit singles since being on The Voice. (Lopez's) career skyrocketed after appearing on Idol, which is fine, but I kind of would like it the other way around, where they do their job and we see the artists' careers skyrocket."
To date, neither The Voice nor X Factor, which offers its winner a $5 million recording contract, has produced a big star. The British X Factor has produced stars (Leona Lewis, One Direction, Cher Lloyd), and Cowell says he will be disappointed if it doesn't generate any here; Burnett trusts that a singer will break out from The Voice.
The right mix of judges/coaches and contestants will be important in the ratings competition, says Brad Adgate of ad firm Horizon Media. Last season, The Voice averaged 15 million viewers on its Monday shows (15.9 million counting the post-Super Bowl audience) and 11.3 million for its Tuesday shows, while X Factor averaged 12.7 and 12.6 million, respectively, for its Wednesday and Thursday shows.
"It's going to be one of the most closely watched battles in the fall," he says. "Who's going to flourish? Ultimately, it may come down to how good the talent is."