The theme of Tuesday night's (April 20) "American Idol" was songs of inspiration, and guest mentor Alicia Keys did her best to offer some positive encouragement to the top seven. The inspirational songs were a setup for Wednesday night's star-filled "Idol Gives Back" special, and in the end, leading contender Crystal Bowersox brought down the house with a performance that instantly felt like one of the show's all-time greats.

The hour began with Casey James taking on Fleetwood Mac's iconic "Don't Stop." Keys said he had to find a way to connect with it and make the crowd remember him and not the song, since the 1977 original was such a huge, well-known hit. Tossing his signature bluesy grit on the vocal, James slowed the pace down just enough to make it his own and ripped off a pair of mini electric-guitar solos for good measure. He even did a little vocal ad lib near the end — "you better be lookin' ahead, not lookin' back, yeah, yeah" — to give it that extra dose of James soul.

For Randy Jackson, it was good but, once again, more of the same, and Ellen DeGeneres said it was time to be great, and he just wasn't. "I don't think anyone is going to be talking about that tomorrow," she said. It was too jam-band for Kara DioGuardi, who said the solos made him seem generic, and Simon Cowell was blunt when he opined that Casey showed "zero emotion" and that there was nothing particularly inspiring about the lazy song choice.

Simon & Garfunkel's "The Boxer" was personal for Lee Dewyze, who said he remembered it from his childhood, when it inspired him to play guitar. Keys told him to recite the lyrics and remember what they mean while he sang. Dewyze played it as a dramatic acoustic ballad while backed by a string section, pumping up the emotion and turning the lyrics into an urgent plea.

Ellen felt the arrangement showed Lee's depth and talent, and DioGuardi said it was clear from his performance that he had a connection to the song, which for her made it his "moment" on the show so far. "That was sincere, that was emotional, that was inspiration," Cowell said, noting that he never particularly cared for the original. "I thought it was absolutely brilliant."

What do you say to a guy like Tim Urban who has had such a hard time on the show, and who picked "Better Days" by the Goo Goo Dolls? Not much, actually, as Keys said Teflon T found a way to make it sound like it was his song already. Also backed by a string section, Urban wobbled through the first bit, strumming his acoustic guitar with his eyes closed, never quite finding the right notes after seemingly hitting his stride last week with Elvis' "Can't Help Falling in Love."

From a banana to soup, Ellen was back to her food metaphors, saying that Tuesday night she wasn't hungry. "I've liked your soup, I have, but today I just didn't like the soup," she said. It was just OK karaoke for Randy, and Simon said the performance wasn't quite believable and a letdown from last week.

Aaron Kelly was 5 years old when R. Kelly released "I Believe I Can Fly," and Keys said it was a big task, but if A.Kells could practically break down by song's end, he might have a shot. Kelly was a bit too somber, and though he hit most of the notes and had a major diva run at the end, the intensity and emotion seemed to be missing.

Jackson and DeGeneres praised his huge voice and said Kelly pulled it off, but Cowell wasn't totally buying it. On the one hand, Simon said, he could judge it knowing Aaron and liking him, which made it seem quite good. "In the real world, if we'd have heard that on the radio, I would have turned it off within 10 seconds," he said to a chorus of boos. "Because it wasn't very good, but you kind of made it quite good."

Pulling off Mariah Carey and Whitney Houston's "Prince of Egypt" song "When You Believe" was not going to be easy for Siobhan Magnus, but when Keys heard the big falsetto note Siobhan had planned near the end, she thought that could be the clincher. Magnus appeared to pull it off, putting some diva power into the song and hitting that high, clear note Keys loved so much at the end.

"Technically, it may have been really well sung, but my problem is it's not a musical, and it started to feel very dramatic," DioGuardi said. Calling it the hardest song of the night, Jackson said it was just OK, but Ellen disagreed, dubbing it proof of why Magnus was still in the competition. Cowell felt the arrangement was too old-fashioned and messy, saying he was distracted by the cloth butterflies wrapped around her arm.

Michael Lynche began putting together his list of 200 songs he'd play on "Idol" if he made it, and the one he picked Tuesday night was Nickelback's "Hero." He played the "Spider-Man" hit as a symphonic acoustic rave-up, giving the muscular rock song a tad more soul.

Kara wasn't feeling it and sensed Mike's tone didn't fit the song, rendering it unrecognizable, though Simon thought he sang it well, even if he came off as artificial and not as authentic as last week.

The primo final spot belonged to front-runner Crystal Bowersox, who chose Curtis Mayfield's legendary "People Get Ready" as a way of expressing how grateful she feels for her opportunity to shine on the show, just days after it was revealed that she almost quit "Idol." Starting off a cappella under a blue and pink spotlight, Bowersox brought a hush to the room as her crisp, clear vocals cut through the silence. As the band kicked in, she took it to church and hit some soaring, bluesy gospel notes and gave a clinic on how to imbue a performance with passion, breaking down in uncontrollable tears at song's end.

"That was inspirational," said Cowell, who appreciated the emotion after fearing that MamaSox had shut down a bit in recent weeks. "You sang it fantastically, and for me it was in a completely different class from everything we heard tonight." Kara loved that Crystal took a risk and put the guitar down. "MamaSox, you know why they call you that?" she said. " 'Cause you just schooled all those contestants." And Randy? He just gave her a standing ovation.

The next contestant will go home at the end of Wednesday's two-hour "Idol Gives Back" special, unless producers revert back to 2007's inaugural year of the charity event and put off the elimination for a week. Check back here to find out what happens.

What did you think of Tuesday night's performances? Who killed it? Who blew it? Who do you think should go home? Write in your comments below!

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