If part one of the "American Idol" finale left you a little underwhelmed, season 10's two-hour second act shows much more promise, if not for the duets alone.

THR has learned of some very interesting pairings in store for tonight's show, airing live from L.A.'s Nokia Theater. In addition to previously reported collaborations (Jack Black with Casey Abrams, Beyonce with the Top 13 girls), Lauren Alaina will have the distinct honor of trading verses with her very own idol, Carrie Underwood, as will Scotty McCreery with country superstar Tim McGraw.

'American Idol' Finale: Lauren Alaina, Scotty McCreery Fight to the Finish

And in what are bound to be two standout moments that don't involve the final two, James Durbin will take the stage with iconic metal outfit Judas Priest (he sang the band's "You've Got Another Thing Comin'" during the Top 24), and Haley Reinhart, who some thought might get a stay of elimination on Tuesday night, will have her moment with Tony Bennett. Serendipitously, the legendary jazz crooner is gearing up for the release of a forthcoming duets album. In addition, ladies man Tom Jones will appear with the Top 13 guys.

'American Idol': The Best & Worst of Season 10

While Fox will not confirm or comment on any prospective bookings, it's been long rumored that both judges Steven Tyler and Jennifer Lopez will perform on the show, the former pushing his first ever solo single and the latter likely hyping her single "On the Floor," currently No. 6 on the Billboard Hot 100. Sources tell THR Lopez will indeed take the stage, but it won't be alone, and multiple blogs report that Aerosmith's "Dream On" was heard during rehearsal on Tuesday.

Photos: Lauren Alaina's 'American Idol' Journey

Backstage in the press room after the performance show, Tyler would only say that a guitar will be on hand Wednesday should he "choose to play it." As for whether the singer will be joined by his Aerosmith bandmates? The jury's still out. Worth noting: it wouldn't be Joe Perry's first time on the Idol stage. The guitarist played The Kinks "You Really Got Me" with Sanjaya Malakar during the Season 6 finale.

Photos: Scotty McCreery's 'American Idol' Journey

The Interscope contingent will include Lady Gaga (performing "Edge of Glory") and U2's Bono and the Edge (performing a song from the musical "Spider-Man: Turn Off the Dark"), and there looks to be one more surprise by an unexpected twosome: the surviving members of TLC.

As with everything "Idol," all is subject to last-minute change. 

Stoked yet? Tune in to Fox tonight at 8 p.m.  for all the action.