In the mid-’90s, Neutral Milk Hotel was but one of innumerable college bands making scruffy pop albums and touring throughout the States. Formed by Athens, Georgia, resident Jeff Mangum — who was part of the Elephant 6 collective that spawned groups like the Apples in Stereo, Olivia Tremor Control, and Beulah, among others — NMH’s first album, 1996’s On Avery Island, made a few ripples, but when Mangum left Athens for Denver to record the follow-up, he had a more grandiose scheme and sound in his head. As he would later admit in a 2002 interview, he read The Diary of Anne Frank and was overwhelmed to the point of tears by its strength and profound sadness.

That emotional weight was imparted to 1998’s In the Aeroplane Over the Sea. From its cover (a striking image that recalls circuses and medicine shows from the turn of the 19th century) to the music contained within, it was an enigmatic record from the first spin. It struck listeners in a way that few college rock albums could. Mangum and band took to the road, but mounting fandom and scrutiny resulted in Mangum breaking down and disbanding the group. There hasn’t been another Neutral Milk Hotel song since.

Which makes Jeff Mangum’s return to the stage at this year’s installment of All Tomorrow’s Parties — which kicks off Friday in Asbury Park, New Jersey — all the more meaningful. In the time since he unplugged his guitar, a new generation of devotees have emerged, absorbing his words into their own experiences. Talking to a Neutral Milk Hotel fan is akin to meeting a true believer. A full-blown cult of music fans now exist for Aeroplane, with the devoted tattooing lyrics on their forearms (or in the case of a girl recently spotted on a Manhattan subway, a rendering of the album cover art on her shoulder), and fans forming their own bands continue to hold it up as an example of perfected musical vision. The album continues to enthrall, its enigma intact since the day of its release back in 1998. But what makes Mangum’s magnum opus so enchanting?

JEFF MANGUM MADE IT COOL TO BE UNCOOL

When Arcade Fire signed with North Carolina indie imprint Merge Records, frontman Win Butler confessed that it was due in no small part to the label releasing Aeroplane. He wanted his band to be aligned with such an album, and listening to his own band’s own body of ambitious, strident, heart-stirring albums, it’s easy to hear the parallel, the example that Mangum gave to them.

At the end of the Clinton era, could there be anything as awkward and disarmingly sincere as the opening of Aeroplane’s “The King of Carrot Flowers Pt. 2″? Mangum’s proclamation “Jesus Christ, I love you!” gets belted out, his voice cracking at such a line. Yet rather than wander into Amy Grant/DC Talk/Christian radio territory, such a statement of faith bursts into fuzz blasts of guitar, bent horn fanfare, and pummeling drums.

But elsewhere, decidedly non-rock instruments carry the tunes, like singing saw and flugelhorn. Beirut’s Zach Condon borrows wholesale from Neutral Milk Hotel’s Salvation Army band aesthetic while Panda Bear sings about caring for his family, his heart firmly on his sleeve. Mangum’s raw vision and openness gave license to others to pursue their muse, no matter how unpopular and uncool it might appear.

JEFF MANGUM’S MUSIC STILL TOUCHES LISTENERS AFTER 13 YEARS

Initiates and veterans alike are struck by the magical aspect of childhood that infuses In the Aeroplane Over the Sea. From the very first line uttered in Aeroplane opener, “The King of Carrot Flowers Pt. 1,” Mangum casts a spell on his listeners. “When you were young, you were the King of Carrot Flowers,” he sings and strums, evoking childhood and its attendant sensations of vulnerability and despair. The surrealistic lyrics that follow carry through with the slightly illogical perceptions that define such an age, in “how you built a tower tumbling through the trees / In holy rattlesnakes that fell all around your feet.”

So it follows with “Two-Headed Boy,” tapping at the confines of his bell jar, the needle singing in his heart. (And such surrealistic word play continued beyond the album, with his radio shows bearing titles like: “The piece begins with every unborn horse fetus on Earth falling out of the conductor’s face as soon as he steps up to the podium to make his opening remarks.”)

And yet the lyrics go beyond child’s play to the tumultuous emotions and depression that are beneath the surface, the knowledge that childhood ends and in adulthood decline is inevitable. No wonder older listeners continue to find comfort in its lyrics. It’s that tumult of emotions that still resonates well after Mangum pressed the STOP button.

JEFF MANGUM HAS MAINTAINED THE MYSTERY DESPITE THE 24-HOUR NEWS CYCLE

In an era where every thought that crosses our pop stars’ brainpans can be broadcast through Twitter and Facebook, when every sold-out show has innumerable videos posted the next morning, when there’s little chance of privacy, that Mangum continues to stay under the radar is remarkable. Sure, every scrap of live footage from Neutral Milk Hotel’s last tour has been uploaded and any sighting of Mangum results in new hits (a soundcheck in Burlington, VT anybody?), but Mangum’s mysterious aura remains intact.

That he keeps such anonymity while living within the very epicenter of indie rock, Brooklyn, is even more remarkable. Consider that he even played an unannounced performance in a Bushwick loft space in December of 2010 that somehow escaped over-documentation — although a few bootlegs were captured, as you can hear at right.

JEFF MANGUM OPENS UP HIS FERVENT FANBASE TO NEW SOUNDS

With a narrow body of work, NMH fans soon ran out of music to consume like manna. Yet Mangum, even in isolation, continues to be an ardent supporter of outsider music. In 2002, some four years after dissolving Neutral Milk Hotel, when it seemed as if he had slipped off the face of the earth, Mangum began to surreptitiously slink into freeform New Jersey radio station WFMU and weave audio collages that even tested the boundaries of the station. He would mix together field recordings, homemade loops, avant-garde compositions, free jazz outbursts, and old country blues records with aplomb. One playlist ran the gamut from a tape of Inuit children playing a language game and A Hawk and a Hacksaw to a field recording of howling monkeys and a children’s choir singing “I Am the Walrus.” He even released a collection of field recordings of Bulgarian folk music recorded at a 2000 festival.

When he did emerge from hiding in the last year, his first show in public wasn’t about him at all. He appeared at New York club Le Poisson Rouge for a benefit to raise money for fellow singer-songwriter, Chris Knox, who suffered a stroke, and Mangum performed a 25-minute set that featured Knox’s quirky songs first — and NMH’s crowd-pleasers last. Hear his take on one of Knox’s songs at right

JEFF MANGUM RETURNS!

That after more than a decade Jeff Mangum is stepping out from the shadows to play All Tomorrow’s Parties will no doubt be a magical moment for those all converged. Yet the festival has always had a way of bringing such musical recluses out of hiding. The inaugural New York installment of ATP in 2008 was a prime example, with My Bloody Valentine (led by Kevin Shields, yet another semi-reclusive musical genius who has never followed up his greatest album effort) curating and headlining.

So what will it mean for the devout fans come Friday (and Monday)? As one YouTube commenter put it, “It’s like JD Salinger published a new book.” And yet live music is a social phenomenon, uniting beyond what any other art form can accomplish. For two generations of listeners who grew up with Mangum’s intimate voice coming through the headphones, alone in that peculiar sound-world he conjured and feeling they were its sole inhabitant, this is the moment they’ve all been waiting for. When all of Jeff Mangum’s fans come together to sing along come with the sacred scriptures of “Naomi,” “Two-Headed Boy,” or “Holland 1945,” it should be nothing less than magical.