Bluegrass meets jamgrass meets psychedelic rock ‘n’ roll when the Travelin’ McCourys and the Jeff Austin Band get together for a Grateful Ball.

The Del McCoury Band spin off and the former Yonder Mountain String Band mandolinist’s eponymous quartet did just that in a packed-to-the-gills Woodlands Tavern in Columbus, Ohio, and, playing alone and together, treated the sold-out bar to more than three hours of exhilarating roots music that bled into early the next morning.

Though they’re quite different – Austin’s band is progressive and dressed in jeans and Ts, the McCourys are more traditional and don button-down dress shirts with their denim – the groups mesh fluidly to put a ‘grassy spin on the Grateful Dead’s songbook, as they did for the hourlong finale. Cramming double double basses, dueling banjos, twin guitars and mandolins and a fiddle onto the bar’s blotter acid-sized stage, it was a wonder the musicians fit – Austin said the groups had to practice “contortionism” to make it work – and didn’t have a train wreck in the process.

The amalgamated nonet plowed through eight lively Dead songs, from countrified numbers you’d expect (“Cumberland Blues,” “Candyman”) and rockers you wouldn’t like “West L.A. Fadeaway” and “Loose Lucy.” For the latter, Ronnie McCoury switched to four-string electric mandolin to add some wah-wah and MIDI effects to the otherwise acoustic hoedown.

The mandolinists Austin and McCoury were the obvious band leaders. But all nine players got a chance to shine, trading solos – McCoury cueing them with exaggerated blinks of his eyes – and vocal spots. The audience chimed in on a singalong “New Speedway Boogie” and the men on stage were so exuberant during “Man Smart, Woman Smarter,” even the ones without mics sung harmony vocals.

This was preceded by a 70-minute set from the McCourys – Del’s sons Ronnie and banjoist Rob, guitarist Cody Kilby, bassist Alan Bartram and fiddler Jason Carter – whose only fault was a sound system that got muddied up between Austin’s opening set and theirs. With three vocalists in Ronnie, Bartram and Carter, the McCourys can cover a wide rage of material flawlessly, which they did with the Eagles’ arrangement of “Midnight Flyer,” the traditional “Long Black Veil” sandwiched inside Bruce Hornsby’s “White Wheeled Limousine,” Passenger’s “Let Her Go” and Nick Lowe’s “I Live on a Battlefield.”

The Travelin’ McCourys have an inordinate number of tricks in their proverbial bag. The biggest and best, perhaps, is their ability to take contemporary songs such as these and make them sound as if they emerged out of the holler more than a century ago.

The Jeff Austin Band makes so such attempt, instead continuing the progressive take on bluegrass the namesake leader began with YMSB.

Their 70-minute opening set was a raucous affair, the audience as crazed as it would be all evening long as Austin and his three bandmates laid on the gas and cooked with it whether they were playing originals such as “Don’t Give Me Up” or covering the Rolling Stones’ “No Expectations.” Calling his fans “friends” and egging on his bandmates with non-verbal cues, Austin was a fiery showman and their set – the best of the three, but on a bill such as this, that’s relative – was so hot the sound system never fully recovered.

Folks who attended the show should be back to normal within a couple of days.