SIMON’S DESIRE TO do a show in New Orleans predates “The Wire.” In the mid-’90s, he began writing regularly on NBC’s “Homicide,” Barry Levinson and Tom Fontana’s long-running adaptation of Simon’s own nonfiction account of the year he spent embedded in a Baltimore homicide-detectives unit, Simon met Overmyer, a more senior writer-producer with the show. Overmyer owned a second home in New Orleans, as he does to this day, and very soon he and Simon, who had been taking regular trips to New Orleans for some time, found they were talking more about their record collections and experiences in New Orleans than about “Homicide.” It wasn’t long before they were thinking out loud about how great it would be to shoot a show down there. The problem was that they didn’t know what show. “We couldn’t figure out how to pitch it,” Simon told me last fall. “Both of us imagined the pitch meeting, and we imagined trying to explain New Orleans and being unable to. If I could explain it to you sitting here now, I wouldn’t have to do the show. That’s the problem: you literally have to drag whatever executive you’ve got to New Orleans, throw him into a second line”— local parades led by brass bands are followed by a “second line” of dancers who join in spontaneously —“get him drunk, take him here, take him there. It would have to be a lost week: you’re not in America anymore — you’re in New Orleans! We couldn’t imagine being able to do that. In fact, we imagined being escorted off the lot. We laughed about it. We said, ‘Pipe dream.’ ”

Years passed, and Simon went on to “The Wire.” During preparation for Season 4, Katrina happened. Simon told me: “Eric was in Baltimore. We were in the writing stage before filming. And I remember in the office looking at the satellite photos on the Internet of his house. And him going: ‘I think I’m O.K.; I think I’m dry.’ ” A few weeks later, Simon was reading the industry trades and saw that three or four New Orleans shows had suddenly appeared in development. There was “K-Ville,” which had a brief run in 2007; a project Spike Lee was developing with NBC that didn’t come to fruition; a few more. Simon knew they had to act quickly: “I said to Eric, ‘We’ve got to go out right now.’ So we flew out to L.A., and Carolyn Strauss bought the idea of us writing something, ’cause there’s not that much money in the script, not a huge investment. And I think on some level she was being polite. You know, ‘ “The Wire” is good, “The Corner” has been good; I can’t say no to you.’ But I don’t think she got it. I think if you talk to her, she’d be like, ‘They didn’t do a good job explaining it.’ I remember this exchange, which is us trying to explain the Mardi Gras Indians, and somewhere in the middle of the pitch she goes, ‘When you say “Indians,” do you mean woo-woo-woo?’ And we’re like, ‘Yes . . . and no,’ ” Simon laughed. “ ‘Not Native American but, yeah, woo-woo-woo-woo.’ ”

“David and Eric were valiant in their attempt to explain their show to me,” Strauss, now an independent executive producer on “Treme,” told me in an e-mail message. “But I couldn’t seem to get it at all. Because I have complete creative trust in David, I told them to write it.” Simon and Overmyer began discussing possible ideas the following summer, but it wasn’t until the next year that writing started. “David did most of the heavy lifting initially,” Overmyer says. Simon sent him a draft of a pilot that had a provisional set of characters and was about 80 percent of a whole but missing scenes. “He did this on ‘The Wire,’ too,” Overmyer says. “He said, ‘I can’t do the domestic scenes; you do the domestic scenes.’ I always thought, He’s giving me the girlie scenes,” Overmyer says, laughing. “On ‘The Wire,’ he’d say to me, ‘You write the scene when McNulty has dinner with his ex-wife.’ Always the girlie scenes.” Once Overmyer filled in the missing moments, the two began bouncing versions back and forth, revising repeatedly, until, organically, the balance of their contributions to the whole achieved parity. “David and I have a good dialectic,” Overmyer says. “He’s a journalist, and I’m a playwright by trade, so I think he tends to wanting to make larger statements about the city than I do, and I tend to resist that a little.”

By spring 2008, two and a half years after the pilot was ordered, they agreed on a draft that they would take to HBO, beginning what tends to be a perilous stage in the development of a series, when the executives charged with paying for production have their say. “On one script,” Overmyer says of an experience developing a show with a different network, “I counted it up: I actually got 72 separate sets of notes — from the production company, the studio, the network — many of them contradictory.” The most memorable note Overmyer ever received was from an executive very high up at a network. “She said, ‘They’re being so unpleasant with each other.’ And I said: ‘Well, that’s drama. That’s conflict.’ And she actually said, ‘Could we have the drama . . . without the conflict?’ ”

Simon remembers many network notes when writing for “Homicide.” “The notes felt like they were not serving the best possible story,” Simon explained. “Jimmy Yoshimura — Eric worked as supervising producer with him, and I was a junior producer under them — Yosh used to do this notes meeting, call me in and say, ‘Come on, let’s do the antler dance.’ And I said, ‘What’s the antler dance?’ And I swear to God, he would put his phone on the floor, on speakerphone, so you’d hear the voice of the network exec. And with his voice, Jim would approximate a reasonable, ‘Well, that’s a very good note, but if we do that. . . .’ But his body language would begin with his hands up above his head as if he were wearing antlers, like some sort of drum circle, and he would dance around the phone, gesturing obscenely to it, do a little more dancing, but all the while he would be saying, ‘Oh, no, that’s a really good note, we’ll have to consider that. Let me talk to Tom [Fontana], because I think we’re going to do something in another episode.’ Meanwhile, he’d pull down his zipper and stick his thumb through it, and if the guy kept persisting on a note and he couldn’t talk him out of it, Yosh would get down on the floor, close to the speakerphone and. . . .”

Yoshimura claims that there are limits to Simon’s recall. “No, no, no, that was David!” Simon offered the following rebuttal via e-mail: “I will own the origin of this particular gesture if that is Jim’s memory, but in the event that he is trying now these many years later to whitewash his authorship of the sacred ritual of the network-note antler dance, I can only quote ‘The Man Who Shot Liberty Valance’ and John Wayne’s remark to Jimmy Stewart: ‘Think back, pilgrim.’ ”

AT THE CORPORATE headquarters of HBO in Manhattan, on an October morning last year, I met two of the executives who greenlighted production of “Treme”: Michael Lombardo, president of programming, and Richard Plepler, a co-president of the network to whom Lombardo reports.