Jonathan Coulton sat in Gorilla Coffee in Brooklyn, his Apple PowerBook open before him, and began slogging through the day’s e-mail. Coulton is 36 and shaggily handsome. In September 2005, he quit his job as a computer programmer and, with his wife’s guarded blessing, became a full-time singer and songwriter. He set a quixotic goal for himself: for the next year, he would write and record a song each week, posting each one to his blog. “It was a sort of forced-march approach to creativity,” he admitted to me over the sound of the cafe’s cappuccino frothers. He’d always wanted to be a full-time musician, and he figured the only way to prove to himself he could do it was with a drastic challenge. “I learned that it is possible to squeeze a song out of just about anything,” he said. “But it’s not always an easy or pleasant process.” Given the self-imposed time constraints, the “Thing a Week” songs are remarkably good. Coulton tends toward geeky, witty pop tunes: one song, “Tom Cruise Crazy,” is a sympathetic ode to the fame-addled star, while “Code Monkey” is a rocking anthem about dead-end programming jobs. By the middle of last year, his project had attracted a sizable audience. More than 3,000 people, on average, were visiting his site every day, and his most popular songs were being downloaded as many as 500,000 times; he was making what he described as “a reasonable middle-class living” — between $3,000 and $5,000 a month — by selling CDs and digital downloads of his work on iTunes and on his own site.

Along the way, he discovered a fact that many small-scale recording artists are coming to terms with these days: his fans do not want merely to buy his music. They want to be his friend. And that means they want to interact with him all day long online. They pore over his blog entries, commenting with sympathy and support every time he recounts the difficulty of writing a song. They send e-mail messages, dozens a day, ranging from simple mash notes of the “you rock!” variety to starkly emotional letters, including one by a man who described singing one of Coulton’s love songs to his 6-month-old infant during her heart surgery. Coulton responds to every letter, though as the e-mail volume has grown to as many as 100 messages a day, his replies have grown more and more terse, to the point where he’s now feeling guilty about being rude.

Coulton welcomes his fans’ avid attention; indeed, he relies on his fans in an almost symbiotic way. When he couldn’t perform a guitar solo for “Shop Vac,” a glittery pop tune he had written about suburban angst — on his blog, he cursed his “useless sausage fingers” — Coulton asked listeners to record their own attempts, then held an online vote and pasted the winning riff into his tune. Other followers have volunteered hours of their time to help further his career: a professional graphic artist in Cleveland has drawn an illustration for each of the weekly songs, free. Another fan recently reformatted Coulton’s tunes so they’d be usable on karaoke machines. On his online discussion board last June, when Coulton asked for advice on how to make more money with his music, dozens of people chimed in with tips on touring and managing the media and even opinions about what kind of songs he ought to write.

Coulton’s fans are also his promotion department, an army of thousands who proselytize for his work worldwide. More than 50 fans have created music videos using his music and posted them on YouTube; at a recent gig, half of the audience members I spoke to had originally come across his music via one of these fan-made videos. When he performs, he upends the traditional logic of touring. Normally, a new Brooklyn-based artist like him would trek around the Northeast in grim circles, visiting and revisiting cities like Boston and New York and Chicago in order to slowly build an audience — playing for 3 people the first time, then 10, then (if he got lucky) 50. But Coulton realized he could simply poll his existing online audience members, find out where they lived and stage a tactical strike on any town with more than 100 fans, the point at which he’d be likely to make $1,000 for a concert. It is a flash-mob approach to touring: he parachutes into out-of-the-way towns like Ardmore, Pa., where he recently played to a sold-out club of 140.