Sometimes, Letterman is funny. Quite often, he isn't.
But the curious thing I've noticed, on those occasions that I've inadvertently channel-surfed my way onto The Late Show with David Letterman, is that the audience makes no distinction between the two situations. No matter what Letterman says, no matter how lame those "Top 10" lists are, no matter how laboured his puns, they clap and laugh and howl like lunatics.
I'd always assumed this meant the laughter was either canned or came from the throats of the mentally deficient. But after spending 90 minutes locked inside the Ed Sullivan Theatre on Broadway in New York I now know the audience is real, and I understand why they laugh like that. They're scared.
Getting into the studio audience was pleasant enough. While on a work trip, I was walking along Broadway on a steamy Wednesday morning when a tall, black, besuited gent waved me down, called me "Sir" and asked if I fancied a free ticket to be in the Letterman audience.
Sure I did. So after showing ID, queuing to enter the lottery for a ticket, then later calling a special phone number and saying, mysteriously, "I'm on Jack's list", by 3.40 that afternoon I was in.
Or rather, I was in a queue again, standing on a stretch of roped-off sidewalk outside the theatre with 50 or so audience members ready to be entertained by Letterman, who each weeknight gets about 3 million viewers in the US alone. His is the second-highest-rating late-night show in the US, which explains why he's paid about $25 million a year, and makes much more again from licensing and syndication fees.
The first hint of what lay ahead was on my ticket, which carried a picture of a Cheshire-Cat Letterman, and the words "Your laughter and enthusiasm are what make a taping of the Late Show successful. Have a great time!"
One of the "pages" - the platoon of clean-limbed guys and gals in Late Show polo shirts who manage the ticketing and crowd control - shushed for quiet. Pretty, white and in her mid-20s, she bellowed over the traffic noise. She laid out the ground rules (cellphones off, no cameras, no recording devices, no food or drink, spit your gum in the trashcan), then asked us to imagine we were at a party and a police officer strip-o-gram had just walked in the door. Whoop with excitement, she said.
So like trained monkeys, we unleashed a zoo's-worth of high-pitched whoops.
"That was excellent," said our page. "Now never do it again!" On this show, unlike Oprah, laughing was good, clapping was excellent, but high-pitched whooping and whistling were banned.
This is the theatre, she reminded us, that played host to Elvis ("yay!"), to the Beatles ("Woooh!"), to Justin Beiber ("Boooo!").
Then she got serious: "Dave will be backstage, watching you guys to make sure you're alive, that you have a pulse. I know for a fact that Dave has way more material than they can possibly fit into one show, and that they will not hesitate to use the break to cut the best material and save it for a better audience that is more in tune with Dave's humour if they don't think that you're with him.
"You guys aren't going to let that happen right?"
"Nooooo," we yelled, though we were quite careful not to be too high-pitched.
"You're going to laugh at all the jokes, right?"
"Yeeeeeeaah," we yelled, though I, and presumably others, were starting to wonder just how bad these jokes must be.
"It's important that you guys know that whatever Dave says, whatever Dave does, just laugh and play along!"
"Sure, fine, whatever, can we just go in?" we were all thinking but didn't dare say.
"Remember, the more fun and energy you guys have," - she was now shouting so loud I worried the vein in her forehead might pop - "the more fun and energy Dave is going to have OK? So I'm going to ask you one more time: Are you guys ready to see The Laaaaaaate Shooooow!?"
We screamed until we were nearly sick and surged towards the lobby doors. Just as they opened, I noticed that 20 metres further down the sidewalk another page was reaching the end of an identically scripted pep-talk with another crowd of audience members, though he, sensibly, was using a megaphone.
Inside, beyond the dour man with a sniffer dog and a couple of beefy security guys, a line of pages funnelled us towards our seats, giving us high-fives and all the while shouting and waving their arms like they'd just seen Jesus. Inside, the house band was playing something really loud.
My seat was in an upper balcony, with vertiginous views down to a small set overhung with hundreds of lights and teeming with dozens of staff in regulation black, carrying bits of set and rolls of gaffer tape.
The band stopped, but the brainwashing wasn't over. In case we hadn't been listening outside, we were played a five-minute video, presented by Alec Baldwin, which explained once again how important it was that we laughed. Of course Baldwin's script - like the rant on the sidewalk - was meant to be ironic ("Even if you think the joke wasn't funny, laugh now and think about it later ... If the joke still doesn't seem funny, discuss it with your clergyman"). And Letterman has long extracted comedy mileage from doing jokes so unfunny that they're funny.
But by this time, what appetite I had for being amused had been replaced by irritation at a comic so needy that he has to beg for laughs, plus low-level performance anxiety that I might accidentally whoop instead of holler.
Eventually, after even more laugh-coaching from a real-life warm-up comedian, Letterman himself appeared. He ran about the stage, delivered his monologue of crummy jokes and interviewed his guests, who included Jamie Foxx plugging White House Down, and the Backstreet Boys singing a top 10 of puerile reworkings of their lyrics.
It was pretty good fun - even though I could no longer tell which of my laughs were because I was actually amused, and which were the result of the pre-show conditioning. If you want to see the episode, it's on YouTube. What you won't find, though, is the thing that made the whole Letterman experience worthwhile despite the grating pep talks.
The house band, led by Letterman's long-time offsider Paul Shaffer, is brilliant, and when the cameras stopped rolling during the ad breaks, the band played on. Presumably it was to keep the audience in an appropriately frenzied state, and it meant we heard loads of loud, fierce, yet impeccably played covers of songs by the Rolling Stones, Jimi Hendrix, James Brown, Bob Marley and more.
Best of all, during one break, as the band jammed on the riff from Otis Redding's Hard to Handle, Jamie Foxx grabbed a microphone and began scatting over the top before leading an extended call-and-response session with the audience. I didn't even need someone holding up a sign saying "clap!" to get quite excited about that.
■ I fluked a ticket to a show recording by wandering along Broadway at the right time. If you want to plan a bit more carefully than that, go to cbs.com/shows/late_show/tickets/ for details of how to book a ticket before you travel. The Late Show with David Letterman screens in New Zealand on Prime around 11pm weekdays.
- Adam Dudding travelled to New York courtesy of 20th Century Fox.
- Sunday Star Times