In the beginning, there was “The Hank McCune Show,” an NBC sitcom that lasted all of three months in the fall of 1950. McCune is long forgotten, but his show’s chief innovation – canned laughter designed to cue viewers at home to feel amused – has been burned onto the DVD-R of our collective pop culture consciousness. With the success the next fall of “I Love Lucy” and its live studio audience, laughter has become an indelible part of TV’s soundtrack, whether produced by actual humans or by machines.

For nearly 50 years, TV comedy had to feed the laugh track monster with jokes designed to produce laughs every 10 or 15 seconds, if not faster. Occasionally, networks tried laugh-track-free comedies like “Hooperman” and “The Days and Nights of Molly Dodd,” but their failure only reinforced the belief that TV audiences wanted to be told when to laugh.

Then came January 2000 and the premiere of Fox’s “Malcolm in the Middle,” which became a mega-hit while violating that cardinal sitcom rule. It was shot in what’s called single-camera style (on film, no audience laughter, lots of location shooting), as opposed to the traditional three-camera sitcom format (on video in front of a studio audience), but it was so funny that viewers didn’t need to be told it was.

The success of “Malcolm” opened the doors for shows like “Scrubs,” “The Bernie Mac Show,” “My Name Is Earl” and “The Office,” none of which would have gotten the time of day at a network a year or two earlier.

“Malcolm” went off the air in May, and the fall season features an odd schism between the big four networks: All of ABC’s comedies and most of NBC’s are single-camera, while CBS and Fox are airing only traditional multicamera laugh-track sitcoms.

“We didn’t make a decision on style,” insists ABC President Steve McPherson, even though his network used to rely on laugh tracks exclusively.

“We didn’t say we don’t want to do comedies with laugh tracks, we don’t want to do multicameras. We certainly went out there and said we want to break the mold. We feel like the same old/same old is not working, so the traditional three-camera, couch-in-the-middle sitcom just didn’t seem to be breaking out at all.”

CBS’ reliance on the familiar form isn’t a surprise, since it’s worked for them for so long. In the past decade, the network has tried a handful of single-camera sitcoms (“Grapevine,” “Danny,” both short-lived), but its big successes have been shows like “Everybody Loves Raymond.”

“Success breeds success in a way,” says Wendi Trilling, CBS’ executive vice president of comedy development. “We’re the ones who are succeeding with multicamera comedies, so people who have multicamera comedies to pitch tend to come to us.”

What’s unusual is to see Fox – which, after “Malcolm,” went gung-ho into the single-camera business – airing so many multicamera shows, one of them, “‘Til Death,” starring “Raymond” Emmy winner Brad Garrett.

“I love the medium of the sitcom,” says Garrett. “To me there’s nothing like theater. And if a sitcom is done right, it’s really a different play every week. And I love a studio audience. I feed off of that. It gives us an immediate way to get an idea of the scene we’re in. Many times we’ll have a second take or a third take, which will be judged right then and there by how the audience just reacted to the last scene.”

“Even though a studio audience is fairly amped up by the warm-up man and they are under obligation to laugh hysterically, you won’t believe their laughter unless it’s funny,” says John Lithgow, star of “20 Good Years,” NBC’s lone multicamera comedy. In one scene in the pilot, he removes his coat to reveal a pasty middle-aged body covered in nothing but a Speedo, and “when I take off that trench coat, that squeal of laughter was completely authentic.”

On the flip side, “The beauty of single-camera is you can find some more subtleties,” according to Wendie Malick, co-star of ABC’s single-camera rookie “Big Day” and a veteran of comedies in both formats (“Just Shoot Me,” “Dream On”). “It gives you a little more room to breathe a few more subtle moments into it. Obviously, the great thing about having an audience is they just raise the whole energy level and you’re kind of doing that hybrid of theater and film, which was great fun. But this one – this gives you a chance to kind of also land and have some moments that are much trickier to do in front of an audience. It’s a lot more intimate.”

Sometimes, Lithgow argues, single-camera shows can get too subtle.

“My sense is a couple of extremely innovative shows came along, single-camera with no laugh track. People thought, “This is sensational.’ (And now) it’s not new. It gradually became the norm. And to my mind, the only danger of that is that there’s less and less absolute obligation to be funny. Before you know it, you don’t have the rigor of three-camera studio audience comedy.”

Jennifer Konner, co-creator of ABC’s single-camera “Help Me Help You,” tries to fight that mentality, noting the words of her mentor, Judd Apatow: “He used to always say in single-camera, if a joke doesn’t work, then it’s the dramatic moment.”

Still, the kinds of jokes are different. With single-camera you can do more visual humor, more physical humor, humor that doesn’t rely on punch lines at all. As Peter Tolan, co-creator of ABC’s short-lived single-camera comedy “The Job” (and now co-creator of “Rescue Me”) puts it on that show’s DVD set, traditional three-camera shows feel “like they’re written in a foreign language, which now everybody knows. And they’re bored, because they’ve heard the joke setups. Anybody can identify a joke setup now based on what they’ve heard in sitcoms.”

On a more specific level, “You’re limited by sets when do you three-camera,” says Ted Danson, a three-camera legend from “Cheers” who’s now playing a shrink in ABC’s “Help Me Help You.” “You end up talking a lot about that funny thing that happened to you on your way to the office, whereas now, you get to see it. And that – to me, that’s much more fun to see the funny thing happening instead of hearing about it.”

While there have been single-camera successes like “Malcolm” and “Earl” in the past few years, there have been more failures (“Arrested Development,” in spite of awards and critical raves, was on ratings life support its entire run). Given that, is someone like McPherson worried about putting all his eggs in the single-camera basket?

“The traditional laugh track comedies have not been popular (lately) either, so I think comedy is risky in general right now because it’s kind of broken, and I think that’s a great thing,” McPherson says. “You know, five years ago people said drama was dead, and now I think it’s the golden age of drama in broadcast television, and cable, too. So I think it’s a risky time, but that’s a good time. People are taking chances, you know, just like when we were kind of down and out and took chances with serialized shows. I think it’s a time where you need to take chances to hopefully find the next thing that breaks out.”

But for someone like CBS’ Trilling, format is almost besides the point.

“I think it just has to be funny,” she says. “I don’t think people come to shows and say, “I want to watch something that was shot outside and doesn’t have a laugh track.’ They want to be entertained.”