Marvin Gaye and Tammi Terrell, Mariah Carey and Whitney Houston, Dolly Parton and Kenny Rogers -- the very best duets in all their kitsch glory endure, so what's the magic behind a great duet?
That's what ABC's new reality TV show, "Duets," is asking America to figure out.
We're used to other singing competition shows that just bash their contestants' voices, but "Duets" brings forth the novel idea of having the judges, all of whom are established recording artists, sing on stage, helping their proteges compete. Behind the scenes, judges help with vocals and song selection, even fine-tuning some dance moves. Viewers who tune in get to vote on their favorites.
Watch the full story on "Nightline" tonight at 11:35 p.m. ET/PT.
On "Duets," pop sensation Kelly Clarkson, R&B star John Legend, soul singer Robin Thicke and country rocker Jennifer Nettles of Sugarland compete each week with their own hand-picked partners. Show creators are hoping that by experimenting with what makes a duet flourish or flop, a single new star will emerge.
In finding that perfect singing partner, Thicke said it comes down to how both singers respond to the song.
"It's not about singing with perfect pitch or timing, it's about feeling," he said. "All art is supposed to create feeling and if you sing with passion and you sing from your soul then people will feel it."
Simply put, a great duet sounds seamless -- artists call it "blending," when the timber and the tone of two voices come together as one.
"It's like a basketball team," Legend said. "Certain players have certain strengths and certain weaknesses and you try to, through playing together, you figure these things out."
"It's a very selfless thing," Clarkson added. "You're only as good as your weakest link."
Clarkson, who was the first-ever "American Idol" winner when the reality show launched in 2002, knows a thing or two about pressure and tough critics.
"It is 10 years later and I love finding kids who were my age when I started," Clarkson said. "I had no guidance. We didn't have help. Ten years later being able to give that to someone was kind of a cool idea to me."
"Duets" debuted on May 24 and, so far, Nettles and her partners are dominating the competition, landing at the top of the chart each week. Contestant John Glosson, a special events and wedding business owner from Georgia, said singing with Nettles was "crazy amazing."
"I didn't know what it was going to be like," he said. "Then the first note we sing, I'm like, 'Oh my gosh, this may be some money here.' It was like, 'This is going to be great.' It's indescribable, really, to sing with someone like that every week."
But sharing the spotlight is not always easy. Thicke and his "Duets" partner, Alexis Foster, were the first to be eliminated.
"I don't want to share the stage with anyone," Thicke said. "I don't even like having dancers around. I want all eyes on me, baby."
But singing with a megastar can really raise an up-and-comer's game. Contestant Bridget Carrington from Virginia said she has learned a lot from her partner, John Legend.
"His voice, it is so smooth, his technique, I'm just trying to get like him," she said. "It's just the music. Once you turn it on, I turn on. It's like a light switch and I just groove to it."
"Duets" airs Thursdays at 8 p.m. ET on ABC.