Depending on who you ask, Jerry Garcia, like Elvis Presley before him, is not really dead.

And if you ask any of the scores of music fans who'll descend on Marvin's Mountaintop in Masontown, W.Va., this weekend for the 12th annual All Good Music Festival, you'll find out that he's not only alive, but he's still kicking out the jams -- in the form of the 30 or so bands who've taken a page from Garcia's legendary Grateful Dead to create a music scene just as vibrant as the late 1960s.

In fact, the culture surrounding live music that spawned most famously from 1969's Woodstock Festival has, through the years, grown and transformed far beyond the now-nostalgic notion of the Hippie Generation. And just as the culture has outgrown cliched tie-dye and peace signs, so, too, has the music expanded, ever twisting and developing into a near-boundless collective of like-minded musicians often held together by only one thread: the jam.

These are not your Top 40 pop songs.

The jam bands that will take the stage at the All Good Festival, while falling under the same improvisational music umbrella held by the Grateful Dead, come from wildly different musical backgrounds. The whiskey-swillin' blues of Gov't Mule hits the stage just a few hours after the hard-driving jazz-funk-fusion of Lettuce on Friday night; Sunday's set of Railroad Earth's mind-bending bluegrass comes after a night of Bassnectar's dark, thumping techno-trance.

So, then, aside from the familiarly friendly jamming of the long-defunct Grateful Dead, what exactly does it mean to be a jam band in 2008, four decades after the hippie scene exploded from underground phenomenon to cultural icon?

Although a casual listener would likely describe a jam band by referencing modern acts such as Phish or Dave Matthews Band, citing long-form songs and wiggling, complex guitar solos over earthy, funky rhythm sections, according to some bands on the All Good bill, the label means absolutely nothing.

Billy Martin, for one, is tired of the term altogether. Percussionist for the grooving progressive jazz trio Medeski, Martin and Wood, Martin's musical background lies in the 1980s New York jazz scene. With a thorough schooling in America's truest jam band music, improvisational jazz, Martin feels that the term "jam band" is simply hollow and meaningless in the musical spectrum.

"The jam band thing, because it's become a category of music, gives the idea of improvising but little else," he said in a recent interview. "There are a lot of bands that work really hard on their music and their sound, but there are others that don't work at all and just noodle around, making a very light sound that's as bad as any smooth jazz I've ever heard. And it's all called jam bands?"

From a musician's standpoint, Martin's qualm is understandable -- why be lumped in with dissimilar bands simply because they all favor improvisation over three-minute pop tunes? One can hardly imagine The Sex Pistols feeling at home grouped with Fall Out Boy, both falling under the banner of punk.

For Martin, though, it's more a discomfort with the label itself.

"You journalists have to come up with a better phrase -- rock 'n' roll is cool, jazz is cool," he said. "Jam band ... not as cool."

Most bands in the scene feel ambivalent toward the term -- "It's because nobody really knows what to say about the stuff," said Railroad Earth's mandolinist John Skehan -- preferring to focus on the uniting factor in the jam band base: the emotions expressed through free-form jamming.

"Some bands play the same show night after night. And some of those shows I'd love to hear -- just not five or 15 times," said Warren Haynes, guitarist and vocalist of festival headliners Gov't Mule. "But part of improvisational music is that people want to come back, because the shows are different every night."

North Carolina native Haynes is no stranger to a recurring audience -- before founding soulful blues-breakers Gov't Mule, he was drafted by the reunited Allman Brothers Band (arguably the second in command of the jam band royalty after the Grateful Dead) and has toured with them on and off since 1989.

To Haynes, it's this element of surprise, of pure, on-stage inspiration and experimentation that tie together his cast of Southern guitar junkies with an act like the reggae and dub influenced SOJA or the new wave art-pop of New York trio Brazilian Girls as all three take the All Good stage.

"Some songs just seem to say, 'Let's go on an exploration for a little while,' " Skehan said of his band's rootsy bluegrass bombast. "And if the song doesn't want to be a big jam, it won't be."

The same could be said for just about any act under the jam band classification -- for every wild, winding "Mountain Jam" that the Allman Brothers bashed out, there was a short and sweet "Melissa."

But while every genre and its surrounding scene are tied together through the years by some unifying factor, time undeniably changes things.

After all, it's been a long, strange trip since the summer of love.

Few bands sense the passing of the jam band torch like Dark Star Orchestra. The collective of seasoned musicians have spent the past decade playing to sold-out crowds with their own retooling of actual Grateful Dead shows. The band's show at Carnegie Library Music Hall of Homestead last winter, for example, was a song-for-song re-creation of the Dead's Aug. 20, 1983, show in Palo Alto, Calif.

In that way, DSO straddles the old with the new, uniting a generation brought up to revere the Grateful Dead as forefathers with a generation who grew up right along with Garcia and company.

"The scene is different in a lot of ways. Technology has made things much different in terms of how and where people will travel. The economy is different -- as I sit here pumping $4 a gallon gas," said Rob Koritz, one of DSO's two percussionists. "But at its core, it's still the same thing as when I was on tour with the Dead [through Europe in 1990]. It's a bunch of people there for the music first, traveling to shows, meeting people and enjoying life and this lifestyle."

And just as bands continuously find new ways to experiment and improvise, building upon the music that's come before, so does the scene surrounding today's jam bands find new ways to connect with the music and with each other.

That said, there are few places where more organic musical and personal communication can be found than one of the many three-day jam band festivals that have, in the past decade, grown from hippie subculture hangouts to some of the most expansive gatherings in modern time.

Just take Bonnaroo. This music festival in Tennessee began in 2002 with a lineup including some of the finest jam bands around (with headliners like Phish's Trey Anastasio, Phil Lesh and Friends, and Ben Harper) and sold more than 70,000 tickets. In the years following, Bonnaroo's annual lineup steadily packed bigger acts -- this year's top billing included Pearl Jam and, oddly enough, Metallica and Kanye West -- giving smaller jam bands more mainstream exposure at one time than any other outlet.

With Bonnaroo taking the lead, the classic hippie music festival has seen an explosion of new ticket-holding music fans often showing up just for the mainstream headliners, but leaving with a laundry list of new, more underground jam bands to check out.

The exposure has, in some circles, blown the doors off a formerly tight-knit community of like-minded neo-hippies, flooding it with fresh faces -- some thirsty for new music and some just there, well, to see Metallica play "Enter Sandman."

Still, the atmosphere at a multi-day music festival is one of musical cross breeding and fan experimentation, both legal (checking out a new band) and illegal (well, you know).

With most festivals inviting music lovers to camp out on the grounds, thousand-tent cities spring up for a weekend and just as quickly vanish, creating an insulated, music-fueled world for just two or three days before kicking everyone right back into the real world.

"It's a commitment," said Martin. "It's not just a concert, but a camping trip, night and day and night and day."

For Haynes, it's the chance to play with a wide cast of characters that keeps festivals exciting.

"During our last Bonnaroo performance we had John Paul Jones and the guys from Hot Tuna play with us, along with Bob Weir [Grateful Dead] and Luther Dickinson [Black Crowes]," he said. "With all those people in one place ... it can get awful crazy."

In a band like Railroad Earth, with its bluegrass thump most at home tearing through the woods, festivals give the band the perfect setting to catch up with friends and sound better than ever.

"Often, it's the first time you may be in the same place for more than 16 hours. We're at a festival for a couple of days, so it gets to be a family reunion with our friends in other bands," said Skehan. "Plus, our music just reaches farther than the walls of a club."

Without the musical precision offered by a club or theater's acoustics, bands are forced to work harder to win over crowds sometimes numbering more than 50,000, let alone comprehend the size of it all.

"Bonnaroo, for example, is enormous. There were 1,250 porta-potties. I mean, just think about that," said Koritz.

Martin shares the sentiment.

"It's hard to get into my little world of music where I can hear a pin drop -- at a festival, you couldn't hear a pin drop to save your life. So you gotta hit it, you gotta groove and deliver that thing you do, just a little bit less intimately," he said.

Similarly, with so many bands to fit over the course of a festival, acts may be forced to squeeze a normal four-hour set into a 90-minute time slot. Luckily, many acts simply see the time crunch as a challenge.

"There's some kind of buzz, this adrenaline rush when there's a huge mass of people there to watch you jam. We still want to take fans on a ride, we just have to do it in a shorter time," said Koritz.

Ultimately, though, it's not any certain headliner or new breaking band that makes a festival. It's the vibe circulating throughout the crowd -- be it of 1,000 diehards or 80,000 casual listeners -- that reverberates back on the bands to make for an outstanding performance, in turn bouncing back to the audience, creating a cycle that can define the success of any festival.

Compared with the oft-surprising variety of bands at festivals such as Bonnaroo or last weekend's Rothbury, All Good's consistent lineup of bands year after year (you won't find the latest indie rock sensation here) creates an atmosphere less sensationalized and commercialized.

And for All Good founder Tim Walther, that's exactly how he wants it.

"Coming from the parking lots of Grateful Dead shows, I was looking to keep that spirit alive -- that family feeling. A place for kids to experiment in a safe manner, where there are people watching their backs," said Walther.

Originally founded 12 years ago, All Good was the creation of jam-band promoter Walther and two friends who'd long been working with the same cycle of bands in the Baltimore and Washington, D.C., area. With little capital to work with ("It was more of a co-op. Bands got paid from the profit at the door," said Walther) the first festival drew 1,000 fans managed by a staff of only two.

Slowly expanding in the years following (All Good now regularly draws upward of 20,000 fans and is staffed by more than 500 people), the festival maintained its family-and-friends-run atmosphere by booking a steady lineup of bands that attract both dedicated die-hards as well as the new and curious festival-goer without bringing in an over-abundance of either.

"Even at 20,000 people, you're still part of the event -- part of the family and community," said Walther. "The first night might feel like a show, but by the second day, you let go of all the world's problems and find the escape that people are looking for."

Its doors far from blown open by mainstream exposure, the festival remains a haven for the jam band faithful.

"The hallmark of the jam band scene is that the fans are people who are not casual music listeners. They are very serious about hearing live music -- going to see a show is something they almost design their lives around. It's not just a vacation, it's a sacrament," said Skehan.

And for some, Tim Walther included, it's a sacrament being upheld and passed along since The Grateful Dead took on San Francisco four decades back.

"All Good could've taken place in 1969 and worked," said Walther, pausing with a reverence for the time and band that started it all.

"Probably would've worked much better."