Andrew McMahon, the 28-year-old Orange County-bred songwriter behind the bands Jack's Mannequin and Something Corporate, is just happy to be here. In 2005, just before the release of the first Jack's Mannequin album, he was diagnosed with acute lymphoblastic leukemia — which was treated, among other ways, with a stem cell transplant from his sister Kate.

The singer-pianist has gone on to have two albums (Everything in Transit and The Glass Passenger) perform well on the charts, make a documentary about his struggles, write songs with Tommy Lee, make noise by reuniting Something Corporate and, in 2006, launch the Dear Jack Foundation, a charity benefiting the Pediatric Cancer Research Foundation, the Leukemia and Lymphoma Society and the Children's Hospital Los Angeles.

It's the latter effort that will see him fronting both his bands on the same stage tonight. On a bill with Marc Roberge of O.A.R. and singer-songwriter Matt Nathanson, Jack's Mannequin and Something Corporate mount a big fundraiser for the foundation at the El Rey Theatre.

He tells our sister paper OC Weekly that he's especially proud of “being able to be there for the patients and other people that are struggling”:

“I'm proud to say we raised hundreds of thousands of dollars in the course of the five years or so that the charity has existed. We've donated that money back to projects and research that impact the lives of cancer patients, leukemia patients and so on.”

It's the first such fundraiser for his foundation and, he says, hopefully not the last. As with most of his post-treatment life, he embraces projects as they come. “I try not to really think about the future,” he says. “It's never been a huge factor in the way that I make decisions. I try as hard as I can to live in the moment.”

Elsewhere: Usher, who laid two releases on fans this year (the album Raymond v. Raymond and four months later the Versus EP), hits Staples Center, supported by Trey Songz. … NYC indie-poppers Freelances Whales, along with Miniature Tigers, play the Troubadour. .. And Bay Area rapper E-40 holds forth at the Key Club.

Also: Olin and the Moon and Wires in the Wall at Spaceland; Pepper Rabbit, Hands, Square on Square and the Silent Comedy at the Echo; Joshua Radio and Good Old War at the Music Box; Lifehouse at the Gibson Amphitheatre; John Carpenter at 3 Clubs; Katherine Jenkins at the Wiltern; Reggie Watts at Largo; Tygers of Wrath and Wake Up Lucid at the Silverlake Lounge; Fiction Plane and Music for Animals at the Viper Room; Dustin Wong at the Smell; Jules Larson at the Hotel Cafe; and Willy Porter at the Mint.

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