Back before jam bands were called jam bands, there were the Grateful Dead and the Allman Brothers. The former rolled and the latter rocked, albeit with a heavy drawl. The bands weren’t particularly close. Jerry Garcia and Gregg Allman even had a spat or two in the media.

Four decades later, both bands are still thriving, thanks in large part to their common denominator, Warren Haynes. The Asheville native and musical workhorse has shared lead guitar duties with the Allmans since 1989 and toured with The Dead, playing Garcia’s licks as recently as 2009.

For the last 20 years, however, Haynes has poured his best original material and heaviest-hitting guitar licks into Gov’t Mule, a side project he began with deceased fellow Allmans alum, bassist Allen Woody. After that monumental figure — famous for his monstrous walks up his bass’ neck — passed away in 2000, Haynes and drummer Matt Abts reconfigured the group with a rotating cast of bass players who paid tribute to Woody in new recordings and on stage. Mule was now the one outlet where Haynes could unleash raw and unfiltered solos over a heavy shuffle, with no pressure to share the stage with another lead guitarist.

In 2004, the group added keyboardist Danny Louis before settling into a quartet with bassist Jorgen Carlsson in 2009. They released their most recent studio effort, By a Thread, that year. Four years later, Haynes is ready to shift the emphasis back to Mule after touring extensively in 2011 and 2012 with his solo band.

“Each project stands on its own merit,” Haynes says from his home in New York. “People that take music very seriously tend to, on a day-to-day basis, listen to music according to how they feel. I’ve always been that way myself.”

He adds, “One of the things I don’t take for granted is that I have the opportunity to do all of these different projects, because I think that some musicians get frustrated and feel like they’re trapped in one certain thing.”

Haynes is a master at the quick transition. At this weekend’s Wanee Festival in Florida, he’ll perform with both Mule and the Allmans in succession, before hopping on the bus to kick off Mule’s tour in Charleston.

“The transition from one project to another comes pretty spontaneously,” says Haynes. “It’s more mental than anything else. You just adapt to the environment. When you get together with a certain group of musicians, energy starts flowing. But each project does kind of influence the others. They’re all breathing new life and being influenced by the others, like an osmosis.”

Mule returned to the studio this winter to record Shout, their first studio effort since By a Thread. Scheduled for a tentative September release, the disc marks a break from Mule’s usual habit of recording at Willie Nelson’s Pedernales Studio in Austin. They opted instead to convene at Connecticut’s Carriage House Studios, an option that let Haynes return home at night to be with his wife, SiriusXM DJ Stefani Scamardo, and their 1-year-old son, Hudson.

“We wanted to do something for a little change of pace and change of scenery,” says Haynes, who hints at “some very exciting stuff I’m apparently not supposed to talk about yet” on the album. (By a Thread featured Billy Gibbons on the ZZ Top-esque “Broke Down on the Brazos.”)

Shout also marks the band’s first recordings as a cohesive quartet, and the album features several co-written compositions, worked out over sessions at bassist Carlsson’s home in California. “There’s definitely a lot of camaraderie,” says Haynes of his Mule bandmates. “When I’m writing, I’m always thinking about the strengths of the band.”

Some of Haynes’ songs, like his oft-performed “Soulshine,” make appearances with each of his projects. He cites tunes he’s written like “Dusk to Dawn” and “Spots of Time” that overlap between the Allmans, his own projects, and shows with the Phil Lesh and Friends collective. Amid a spring U.S. tour and July in Europe with Mule, he’ll even transpose a set of Dead tunes into arrangements for a 55-piece orchestra, performing in Boston, San Francisco, and Los Angeles.

“I have to really focus on it in a different way because I’ve never worked with a symphony before. It’s a lot of work, but it’s something I’ve thought about doing for a long time,” says Haynes. “I got a call last year from the Jerry Garcia estate saying they were ready.”

Likewise, Mule makes a stop this spring at MerleFest, one of the nation’s marquee bluegrass events, where he says they’ll make an effort to showcase the band’s “lighter, more melodic side.” But it will not be an acoustic show, he clarifies. That just wouldn’t be Gov’t Mule.

And in Charleston, fresh to the stage with their studio recording work wrapped up, Haynes says they’ll be fully plugged in and not holding back. “Charleston is the first official show of the tour, so we’re going to be ready to rock,” says Haynes, who will be out on the road with Mule from this weekend until August. “This is where it starts.”