On the day before Halloween, nearly six months after we were first puzzled by the slo-mo Mister Softee jingle invading the sidewalk Wi-Fi tablets of New York City, I received a cryptic email that began as follows: "I'm the one who's been making the LinkNYC kiosks blast Mister Softee, and other noises and sounds. I'm contacting you through a burner email address, because I don't think I want to identify myself as the culprit. You might understand my indecision better if you knew who I am. Or maybe not. I don't know."

The email was unsigned, delivered only under the moniker "stupid city." It contained a 2,000 word manifesto outlining the motives and methods for the writer's ongoing manipulation of the ubiquitous kiosks. It was neither a prank nor a hack, he clarified, but something he deemed street theater — "an ephemeral kind of performance art that subverts a repugnant piece of street furniture (LinkNYC)."

I quickly responded to the email to ask for proof of his handiwork, and he suggested we meet in person for a live rendition. After a period of contemplation, "stupid city" agreed to let us share his identity, so long his face wasn't visible in any photos. Likewise, I only briefly considered the possibility that I was living out a Stephen King horror novel, soon to find myself locked in the freezer of an ice cream truck, my final cries blotted out by the somnolent jingle.

From the moment the nine-a-half-foot tall screens began springing up on city sidewalks in early 2016, promising free gigabit speed Wi-Fi and domestic calls, Mark Thomas said he saw their alternative application as a broadcast platform. In the years since, he's conceived dozens of soundscapes, including his own experimental noise pieces, spoken word poetry and spooky piano compositions. He observed MLK Day by playing the "I have a dream" speech along Broadway in Astoria, and once held a curbside memorial honoring the passing of radio legend Joe Frank through four machines at once.

But it wasn't until earlier this year that Thomas hit on sonic gold, with his eerily slowed-down take on the familiar Mister Softee theme song. "It sounded irritating and bad," he explained. "I decided to stick with it." As time went on, he added air horns and numbers sequences that offered clues to his identity.

Throughout the summer, befuddled pedestrians shared videos of the howling tablets online, some testifying to having witnessed the creepy tune blaring "seemingly in unison" from up to ten hotspots at once. A few people speculated that it was the result of hackers, possibly the Russians, or else yet another intrusive guerilla marketing campaign. A spokesperson for LinkNYC tried to downplay the development, insisting that it was merely "an old fashioned phone prank."

Maybe so. But the strange missive that had landed in my inbox touched on something else behind the haunting broadcasts. "I have what I guess you'd call a set of grievances about the kiosks, and how the company behind them has failed to do anything particularly innovative with the unearned municipal privilege they enjoy with their monopoly franchise," Thomas wrote.

"I have never understood the fundamental premise of LinkNYC, that every single outdoor payphone should be routed and replaced with this unproven alternative, or how such a broad decision affecting the public interest was reached without a single call for public input." (Representatives for LinkNYC disputes this characterization of the community feedback process).

Long before he began tormenting the auditory cortices of unsuspecting New Yorkers, Thomas loved payphones. A self-described "phone phreak," his obsession began in high school, when he'd spend hours in his bedroom dialing a booth on a seedy Tampa Bay street, then playing piano for whatever stranger picked up. As an adult, in the 1990s and early 2000s, he maintained the largest database of payphone numbers and addresses in the world, which he made public on his website in the hopes that others would pick up his teenage hobby.

When the New York Times profiled Thomas in 2004, they found that his Payphone Project had grown into a practical tool for desperate people across the world—a parent searching for her runaway daughter, detectives seeking a predator, etc.—while staying true to its goal of forging "whimsical acts of contact" between strangers. ''Pay phones are lifelines for the down and out; their booths are rainy-day cocoons,'' he'd told the newspaper. ''You lose those, and you lose a lot of windows onto the human condition.''

So it makes an obvious sense that Mayor Bill de Blasio's decision to rip out most of the city's 7,500 payphones and replace them with decidedly less-cocoonish digital obelisks would inspire a very specific grudge in Thomas. The fact that LinkNYC is effectively underwritten by Google, through its subsidiary Sidewalk Labs, which was founded by former deputy mayor and "smart city"-booster Dan Doctoroff, likely did not cushion the blow for the self-identified artist.

But when we finally meet in midtown on a Tuesday afternoon, the 50-year-old Thomas does not appear overly preoccupied with nostalgia or vengeance. He's far more interested in demonstrating his process, which involves using the kiosk's free domestic calling feature to dial one of the countless conference call numbers he's rigged with various pieces. He then cranks up the volume on the device, clicks back to the home screen, and walks away.

Each of his recordings begins with sixty seconds of silence, a detail he added after discovering that people in certain areas, particularly Murray Hill and the Upper East Side, "really hated when the serenity of their neighborhoods were disrupted by noise blasting out of these things." This "magic minute," as he's dubbed it, helps Thomas to avoid detection, while also allowing him to program several machines at once.

Our chosen intersection, 42nd Street and Third Avenue, places us within a one-block radius of eight different machines. I watch as he punches a number into the keypad, then blends into the stream of office workers and emerges at another machine fifty yards away. The spontaneous jingle draws a few gaping expressions and exaggerated double-takes. Mostly, New Yorkers react to the song by stealing only a momentary glance at their surroundings, seeming to acknowledge and then accept the oddity without breaking stride. The reaction is a bit better over the summer, Thomas points out, because sound carries further in heat.

Throughout the demonstration, Thomas, a trained classical pianist and former web developer, seems quietly pleased by his symphony. Ears tuned forward like antennae, he observes how his favorites pieces "tangle in with the rest of the street noise and fill those little washes of silence that come in when traffic has moved on." While there are advantages to the built-in audience of Midtown, he's partial to lonelier kiosks in Sunset Park, and one in particular located under the 7 train in Corona.

If there is an apparent contradiction in the project—his beaming pride in the pieces and simultaneous gripes with the devices themselves—Thomas is not worried about it. He's not particularly focused on fears raised by watchdog groups about illicit data-mining and surveillance overreach either. His core beef with LinkNYC is rooted in the singular fact that they claim to be "the payphone of the future," when their primary purpose seems to be serving up digital advertisements to non-consenting pedestrians.

"I consider the kiosks themselves to be unwanted, unasked for irritants, and to express that sentiment I turned the kiosks themselves into irritants," Thomas explains. But he's also quick to emphasize that he considers his work not as a protest but as a sort of one-man outsider art project, and that he views LinkNYC as "less of a threat than an opportunity." He'd be happy for others to take up the mantle of street theater as well.

Is there a deeper meaning behind his taunting Mister Softee remix? A dissonant clapback at the techno-utopian delusions of the smart city, perhaps? A winking reference to one of the extant targets of Mayor Bloomberg's city-sanitizing campaign? No, not really. He was just messing around on his laptop one day and inadvertently played the jingle at half speed, he says.

Eventually, I ask Thomas whether LinkNYC is aware of his efforts. He believes that they are, and that the company may have even gone through the trouble of rewiring the network because of him. While users were once able to place uninterrupted calls for four hours at a time, the kiosks now require you to confirm that you're still there after 10 (or sometimes three) minutes. It wouldn't be particularly hard for them to find him, he notes, waving to one of the tablet's three cameras.

LinkNYC would not comment directly on Thomas's work, though a spokesperson for the NYC Department of Information Technology & Telecommunications told Gothamist: "Considering that more than five million people have used LinkNYC because it’s fast, free, safe, and useful, it makes sense that among them there’s a prankster."

For now, Thomas plans to continue staging his unique brand of street theater, spreading false hope to ice cream lovers, and pumping countless other works of noise through the towering monoliths across the city. He has many reasons for doing this, but chief among them is that it brings him joy.

"For as long as I can remember, I have wanted to feel invisible yet present, and this is as close as I think I've come to reaching that goal," he wrote in that mysterious introduction. "I feel like a ghost, but at the same time I am hiding in plain sight."