Actor/comedian Ed Helms may have debuted his singing chops to the masses in a pseudo-improvised scene in last year’s The Hangover, but he actually has an interesting musical past of note, having played in a trio in NYC back in the day called the Lonesome Trio. Nowadays (when he isn’t wondering “what tigers dream of when they take a little tiger snooze”), Helms is a bluegrass fiend with his very own festival set to premiere at Los Angeles’ Largo this weekend.

As Spinner reports, Helms recruited Jackson Browne, comedian/banjoist Steve Martin, Gillian Welch, Dave Rawlings, Nickel Creek, and John C. “Reed Rothchild” Reilly for the series of concerts, dubbed “L.A. Bluegrass Situation,” on March 18-22.

And for those hoping for another improvised masterpiece from the comedian-heavy lineup, fear not: “There’ll be a lot of late-night jamming,” Helms said.

As we previously reported, many famous rock musicians and a songwriter for Sesame Street were outraged late last year when news broke that their music had been used to torture inmates at Guantanamo Bay. Whereas Drowning Pool’s Steve Benton said it was “an honor to think that perhaps [their] song could be used to quell another 9/11 attack or something like that,” Trent Reznor, Rage Against The Machine, and many more were understandably furious.

Now Reznor and Rage’s Tom Morello have joined the National Campaign to Close Guantanamo, along with R.E.M., Pearl Jam, the Roots, Rosanne Cash, Rise Against, Billy Bragg, and Jackson Browne, Huffington Post reports.