"The X Factor" Semi-Final with the Top 4 acts delivered plenty of hits for fans eager to see them compete their best on Wednesday.

All four acts performed two songs each-  a Contestants' Choice song selected by viewers at home and a song chosen by their mentor for a chance to make it to next week's season finale.

The highlight of the night came from 13-year-old frontrunner Carly Rose Sonenclar. She sang and played the piano to the John Lennon classic "Imagine." .

"What I love is that you've taken your artistic credibility up one notch by playing the piano," said, judge L.A. Reid, while admitting that he was impressed that she tackled such a beloved yet difficult song to accomplish. "You always go in and find that [high] note, don't you?" he added.

Fellow judge Demi Lovato was concerned that Sonenclar might become too predictable earlier in the show but then retracted her comment when she said, "the only predictable thing about that performance was that it was going to be amazing."[You] sounded really beautiful..Loved that you took a risk."

Simon Cowell called the performance "overcomplicated," because the teen had a choir to back her up but her mentor Britney Spears disagreed. "It is time for you to go beyond this stage and compete with the biggest stars in the world," she told her contestant.

The other highlight of the night came from one of Simon Cowell's two groups that are still in the running, Emblem3.

The boy band performed an impressive spin on Peter Frampton's "Baby I Love Your Way" for their Contestants Choice song. The rap and reggae-inflicted take on the Frampton classic inspired Reid to call it their "$5 million moment." "That is the first time I really saw you as recording artists," he added.

Spears called their take on it "special." 

"If this doesn't get you into the final, nothing will," their mentor Cowell said proudly.

Cowell chose the Beatles' classic "Hey Jude" for their second song performance. Reid commented that doing a Beatles song was very "presumptuous," but added they are "teen heartthrobs" like the Beatles.

Spears said it was an "A-level performance."

Lovato didn't agree. She said the group were not on the Beatles level yet but "they're getting there."

"Guys, I just feel so proud of what you've achieved here tonight" Cowell said of his group, adding that they "nailed" both songs.

"The X Factor USA" co-host Khloe Odom couldn't contain her disbelief that the season is coming to an end. "This is crazy!" she said. "I can't believe the finals are next week!"

During the "Live Results" show which will air tonight, only three acts will advance to next week's finals. There will not be a sing-off between the Top 4 and none of the judges get to pick their favorite acts during the "Live Results" episode, said Lopez. The elimination will be based purely on viewer voting.

The "Live Results" elimination show for the Top 4 contenders for Season 2 of "The X Factor" will air live on Thursday, Dec. 13 at 8/7c on FOX.

Watch Carly Rose Sonenclar perform John Lennon's "Imagine" in the video below

Watch Emblem3 perform 'Baby I Love Your Way" in the video here