Just like country night, the disco round of "American Idol" can separate the contenders from the also-rans. And, Tuesday night, that's pretty much what happened.

Unlike last week, when the judges had to give their comments in pairs because the previous week's show ran over, this time all four judges had their say. The resulting news was not good for frequent bottom-three dwellers Lil Rounds, Matt Giraud and Anoop Desai, while front-runners Adam Lambert, Kris Allen, Danny Gokey and Allison Iraheta once again nailed it. Either way, two contestants will be going home on Wednesday night (April 22).

Rounds was up first, wearing a skintight black bodysuit and singing Chaka Khan's "I'm Every Woman." She hit the funky grooves of the classic disco anthem and looked loose and comfortable as she worked the crowd.

But, alas, the once promising 23-year-old seems to have permanently lost the judges' eye, as Randy Jackson said the song sounded too "wild" and didn't really show what kind of artist Rounds would be. Kara DioGuardi lamented that like all of America, she was waiting for Rounds to sing something by an artist like Khan, but, unfortunately, she wasn't sure it had been worth the wait.

"You've been every woman on that stage during this competition," she added, "every other woman but yourself, and tonight you still didn't tell me who you are as an artist." Regardless of what the judges thought, a dejected-looking Rounds said she had fun, which was good, Simon Cowell said, because he's pretty sure it's the last America would see of her.

Not looking as boogie-ready, Kris Allen said he was worried by the genre, so he picked "She Works Hard for the Money" by Donna Summer, switching it up Santana-style with a stripped-down arrangement on acoustic guitar. Channeling John Mayer more than the disco queen, Allen, accompanied by a pair of percussionists and a bass player, turned the dance-floor anthem into a salsa-fied soul tune.

Kara loved it, and said his risk-taking paid off big-time and the song could appear as is on Allen's debut album. Simon called Allen's interpretation original, the polar opposite to Rounds' performance and decidedly not karaoke.

Danny Gokey went the Earth, Wind and Fire route, singing a bouncy, reverent version of the roller-boogie hit "September." Of course, he gave the horn-heavy song a bit of a gospel shakedown via his sandpaper-and-silk vocals, and he tossed in a few more dance moves than he's shown to date.

Randy wasn't sure about the song choice, but praised Gokey for taking a song with narrow melodic range and making it his own. Kara, calling him an "incredible vocalist," said his pitch was, as usual, spot-on, though she wondered if she'd remember the very by-the-numbers arrangement at night's end. After Paula praised his very sexy voice, Simon simply agreed with everyone else, saying the vocals were strong, but faulting Gokey for not showing off any star power in the performance, which he called awkward and clumsy.

Allison Iraheta started off sitting on a lit stairway for a sensual take on Donna Summer's "Hot Stuff," but then stood up and strutted the stage in a skintight black-and-silver dress and shiny black leggings for a roughed-up, almost goth-rock take on the dance classic.

Kara and Randy weren't crazy about what they dubbed an overindulgent arrangement, but they once again praised the 16-year-old for being one of the best contestants in the competition. Saying she was always destined to come in as the underdog this week, Simon said the song was simply "brilliant."

What would Adam Lambert pull off this week? Dressed conservatively in a black suit and black tie and with his jet-black hair pushed up into a pompadour, this year's breakout singer took on Yvonne Elliman's "If I Can't Have You," turning the Bee Gees-penned dance tune into a slow, sensual ballad full of heartache and longing (and a few of his jet-scream wails).

"You are ready right now!" Randy huffed, giving stage veteran Lambert props for mixing it up every week and showing the judges and audience so many different musical looks. "Adam, you're brilliant," Kara added. Calling the emotion he put into the song inspiring, Paula was again near tears, applauding his decision to avoid cliché.

"I felt your pain; I felt your vulnerability, which was beautiful," she said. "It's as if you tore your heart out and left it on the stage. You're fascination, you're brilliant, you're awesome, and you will be in the finals." Simon couldn't quite feel the pain, but was stunned by the one-of-a-kind, memorable arrangement and "immaculate" vocals. And, once again showing his class and professionalism, Lambert praised the collaborator who helped him come up with the arrangement.

Things did not go as well for Matt Giraud, who survived last week's show by obtaining the first-ever judges' save. Singing the Bee Gees' "Stayin' Alive," Giraud brought back the mini-fedora and a slightly herky-jerky persona that was reminiscent of 2007's beat-boxing runner-up, Blake Lewis. With lots of whoops, falsetto wails and gospel groans, Giraud ended on a shaky high note that might have sealed his fate for good.

For Randy, the song choice and arrangement were off, though he said Giraud showed his huge singing talent. Kara liked how he brought the mood back to disco after a relatively sedate slate of covers, while Paula promised that unlike last week when the judges bailed him out, this time Giraud saved himself.

The news was not as great from Cowell, who said, "I think you've got to get yourself out of 'Idol'-land for a moment and put yourself in the real world. In the real world, that, to me, came over as a bit desperate. I didn't think the vocals were great. I didn't hear any originality."

Anoop Desai closed things out with yet another Donna Summer tune, the melancholy "Dim All the Lights," bringing back the smooth 'Noop Dogg persona while rocking a gray suit, pink vest and tie and blue shirt.

Randy faulted the bum note Anoop hit at the end of the performance, but had nothing but kind words for the rest of his vocals. Kara thought the rendition could be on the radio and said Desai picked the perfect song for his tender, silky vocal style. Simon, once again, wasn't onboard, calling the song "mediocre at best" — no, strike that, a "horrible" version of the song — and saying it was Desai's worst performance by far.

Tonight's elimination show will feature music from last season's runner-up, David Archuleta, singing his latest single, "A Little Too Not Over You." Disco legends Harry Wayne "KC" Casey of KC and the Sunshine Band, Thelma Houston and Freda Payne will also be there to perform a medley of their boogie-fever hits, including "Get Down Tonight," "Don't Leave Me This Way" and "Band of Gold."

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