Nashville moved west Saturday night to the Troubadour in West Hollywood, where Dierks Bentley hosted a freewheeling pre-Grammy hootenanny studded with stars from throughout the country-music firmament.

“I’d just like to say that there’s never been a more generous musician than Dierks Bentley,” said bluegrass heavyweight Sam Bush, late into the 2 1/2-hour show, and if Bush was referring to Bentley’s willingness to share his stage time, he may have been right: Miranda Lambert, Blake Shelton, Zac Brown, Del McCoury and all three members of Lady Antebellum performed Saturday, occasionally relegating the evening’s headliner to humble backing-band duty, as in a stripped-down rendition of “Need You Now,” Lady Antebellum’s moody 2010 smash.

The sprawling guest list — which also included such Nashville outliers as Paramore frontwoman Hayley Williams and Dan Auerbach of the Black Keys — reflected Bentley’s expansive approach toward country music. Or at least his newly expansive approach. Last year, following a string of slick country-rock discs, Bentley released “Up on the Ridge,” a scruffier, bluegrass-inspired effort with appearances by Kris Kristofferson, Jamey Johnson and the Punch Brothers, among others. It’s a grasp at down-home traditionalism that feels as lively as Bentley’s more pop-attuned material.

At the Troubadour, Bentley switched easily among those modes, alternating recent hits such as “Sideways” (in which he beseeches a club DJ “to keep those girls out on the floor”) with rootsy standards including Hank Williams’ “Your Cheatin’ Heart,” delivered Saturday as a no-frills duet with Zac Brown. “One for the fans, one for the heroes” was how Bentley explained his method to Lambert, who followed a rowdy version of her “Gunpowder and Lead” with “Silver Wings,” the tender Merle Haggard tune.

Elsewhere, Bentley and his band supported Williams in a lightly countrified take on Paramore’s “The Only Exception,” while actor Garrett Hedlund (of “Country Strong” and “Tron: Legacy”) channeled Kristofferson’s stentorian drawl in “The Pilgrim, Chapter 33.”

Hedlund wasn’t the only representative of Hollywood in attendance: For help doing his song “Down in the Mine,” Bentley brought to the stage Jessi Alexander, who co-wrote the Miley Cyrus hit “The Climb,” from “Hannah Montana: The Movie.” (Before they sang, Bentley recounted a meeting with Cyrus in which he excitedly informed the young singer-actress that they shared a friend in Alexander. Cyrus’ classic response: “Who?”)

The night’s most exciting performance was also its unlikeliest: a three-way jam on several old-timey folk numbers (including “Single Girl, Married Girl” and “Worried Man Blues”) by Bentley, Auerbach and McCoury, the 72-year-old bluegrass veteran whose crisp church-elder outfit made his younger peers look like roots-music ragamuffins.

“We’re not running a tight ship here,” Bentley had said earlier of the show’s willfully haphazard vibe, and it was less an apology than a point of pride.

-- Mikael Wood