'American Idol': Top Four Take on Classic Rock and Sia

American Idol XV - Top 4 - H 2016
Courtesy of FOX

With the series finale only two weeks away, American Idol narrowed the farewell season's contestant pool down to just four artists tonight. As the results of last week's voting were gradually revealed, the top four all had the chance to give two performances. Their first songs were all from the classic rock genre, with guest mentor Steven Van Zandt of Bruce Springsteen's E Street Band lending his expertise in rehearsals alongside BIg Machine Records' Scott Borchetta. Their second songs of the night were all from the catalogue of Sia, who also helped prepare the artists this week and was one of a few guest performers to take the Idol stage tonight.

La'Porsha Renae was the first artist voted through. For her first song, she sang "Wanted Dead or Alive" by Bon Jovi. Renae really dug into the vocals, bringing a little more edge and grit to her tone than she usually does in her ballads. Renae has proved over and over that she can sing anything thrown her way. Keith Urban said she brought out some blues undertones to the song.

Also voted through to the top four, MacKenzie Bourg took on Cheap Trick's "I Want You to Want Me." In classic Bourg form, he came up with his own rendition of the song that showcased his impressive artistry and creative instincts. "You MacKenzied it," Jennifer Lopez said, although she wasn't the biggest fan of his arrangement. Urban doubled down on her criticism and said he hated the arrangement. Bourg would have to prove himself with his second song.

Singing his single "Heartbeat," season-seven winner David Cook performed next. A montage of past Idol moments played behind him, showcasing the 14 singers who have previously won the competition.

As the results continued, Trent Harmon was the next artist voted through. He sang ZZ Top's "Sharp Dressed Man," and his vocals were strong, but Harmon still struggles to look comfortable and natural onstage. Harry Connick Jr. praised his creative choices though, especially how Harmon muddied up the song and changed up the tempo.

That left Sonika Vaid and Dalton Rapattoni in the bottom two. Vaid was voted off the show, and a montage of highlights from her journey this season followed. As the competition nears its end, the goodbyes are getting harder.

Rapattoni initially wanted to sing "Seven Nation Army" by The White Stripes, but Borchetta and Van Zandt encouraged him to change his mind because the song didn't really go anywhere. Rapattoni was somewhat reluctant about changing his song, but he ended up going with "God Only Knows" by The Beach Boys. It ended up being a strong choice. Rapattoni gave a smooth, gorgeous performance that was a little more understated than some of his more theatrical performances, but it was just as emotionally potent. As Connick pointed out, it was also one of the more melodically challenging songs Rapattoni has sung so far in the competition.

Next, season five's runner-up Katharine McPhee reprised her Idol performance of "Over the Rainbow."

McPhee's spectacular performance was followed by the start of the Sia round of tonight's performances. They all got to choose from the many songs Sia has written through the years.

Renae was up first with "Elastic Heart." "She's the kind of artist I want to be," Renae said of Sia, who watched and loved her performance of "Diamonds" a few weeks ago. Renae moved Sia in their rehearsals, and she brought that power to her final performance, which was emotional and captivating. Every week, Renae makes a compelling case for why she should win. Tonight, she delivered the two best performances of the night.

Bourg followed with a performance of "Titanium," and in his rehearsals, he struggled with some of the high notes. But Sia encouraged him to tap into his falsetto and not get too in his head about it. He went for the high note in his final performance, and even though there was some strain to it, the risky move ended up working. Again, Bourg made the song his own and brought a slightly softer vibe to it. Connick didn't like that Bourg made it so much about the one note, but Urban liked that Bourg used the high note very well.

After Sia performed "Cheap Thrills," the competition resumed. Harmon took the stage again with "Chandelier." Sia also pushed him to go for the high notes in the song. Harmon gave a slowed-down and soft performance of the song and was very precise with his vocals. He looked more comfortable than in his first performance, and the song was a better fit. "It was exquisite. I loved every minute of it," Urban said.

Rapattoni closed out the night with an emotional performance of "Bird Set Free." He connected so viscerally with the lyrics, and he was overwhelmed by the end. Rapattoni really released during this performance, and it was powerful to watch. He doesn't have the best voice in the competition, but he brings considerable passion and authenticity to every performance. "You touch all our hearts every time you get up there, but especially tonight," Lopez said.

What did you think of tonight's performances and Vaid's elimination? Tonight's votes will determine the top three, and American Idol resumes next Thursday.