“Hey. You’re not gonna believe what happened earlier today,” Jeff Tweedy told the crowd at Madison Square Garden Friday night. “Listen to this. During soundcheck, these guys in suits came down here, and they were really nice to us, and they gave us gold records. I rode the subway back to the hotel with it on my lap.”

It was hard to believe that Tweedy – who wrote “Screen Door,” perhaps the most accessible rock song ever written, and sang it in a shaky voice on “No Depression” just 15 years ago – was standing there in front of Wilco on the stage of Madison Square Garden on Friday night, New Year’s Eve, all available evidence pointing to the fact that he’s a rock star.

I didn’t think it would happen, even when I bought tickets. I thought I’d be watching a Wilco show with 3,000 people in a huge, empty hall. Madison Square Garden? Are you kidding? Aerosmith plays MSG. New Year’s Eve? New York City? Wilco? They’re a little band. They’re just like those guys in the garage down the street.

But there we were. And the crowd was big and wild. It was a stadium show, thousands screamed, dope smoke filled the air, and somehow it was true: Wilco has ascended. They’re in the Show for real. They’re rock stars.

Rock Stardom, of course, isn’t exactly what it once was. Consider the bra incident.

It happened sometime after midnight. The band was rollicking through a post-countdown set of well-chosen covers. They played Judas Priest’s “Livin’ After Midnight,” then they said the next one was by “Judas and Tennille” and played “Love Will Keep Us Together.” They played “I Shall Be Released.” (I think this was right; it’s weirdly supercilious to just start playing your own music in the first ticks of the new year.)

Then someone threw a bra on stage. Tweedy was noticeably distracted, bemused, by it. After the song was over, and the guitars switched out, he walked over and picked it up.

When he picked it up, we all got a pretty good view, and I can say this: That was one sensible, clean, and sturdy undergarment. It was not, decidedly not, of the lacey, sexy, decolletage-enhancing type groupies wear when they want to get backstage. This was verging on foundation garment.

“Now why would you do this?” Tweedy asked. “Just when I was going to dedicate the next song to my wife.” Then he joked that it hadn’t been for him after all, but for bass player John Stirrat, making light of the presumption that a bra hurled to the stage is intended for the front man.

I appreciate that the band is doing battle with its own presumption; next month they’re playing at the 9:30 club in Washington, D.C. I remember the comments they made when they played Summer Stage and Sonic Youth opened up for them. Peculiar, they said, to have a band to whom you listened open for you, like Bo Diddley opening for the Rolling Stones. Everyone involved must want to stop and say: “Hey, no, other way around.” But it’s okay, because everybody likes everybody else’s songs.

Wilco seemed comfortable in the spotlight. They occupied the stage as if they belonged there, and used the massive wattage of the MSG sound system to full effect. But clearly it was not lost on them that they were playing Madison Square Garden. They were consciously self-effacing about the whole thing. Tweedy was wearing pajamas.

Wilco soaks itself in a friendly spirit of anti-aggrandizement. Just watch keys/guitar player Pat Sansone do his rock ‘n’ roll faces and play windmills on the Telecaster. It’s the epidemic of my generation, to celebrate and deprecate simultaneously. You can move like Pete Towsend, but you have to know that you’re moving like Pete Townsend. You can be a rock star as long as you don’t derive too much self-confidence from the limelight.

In some contexts – the super genius dork writer context, for instance – this is annoying. Up on stage, it is incredibly winning.

I still think about songs like “Passenger Side,” from Wilco’s first record, a song about getting a ride to the bank because you got a DUI. It was simple stuff about people you knew. Along the way, the sound expanded. They started taking fewer cues from the Rolling Stones and more from Brian Wilson and Sonic Youth. They ended up with these incredible, deconstructed pop songs.

And they do sound literally deconstructed – as if you’d taken apart all the instruments and equipment and left it all on, full power, humming on a table in the studio. Then the band walked into the studio and played a pop song over the top of the buzzing, humming, phase-shifted mess of wires and transformers. You think you’re listening to a simple song, then you realize that somehow the melody and the hook dragged you into this crazy whirl of machine noise and feedback.

There is something really wrong about a music world so shattered that a band can fill Madison Square Garden and not get played on the radio. Maybe we’ve hacked the music up into so many subsets that it can’t be properly delivered any more. But why should Tweedy be surprised by the fact that some chick wanted him to have her underwear? Why was he surprised, stunned even, that men in suits showed up and told him “Yankee Hotel Foxtrot” had been certified gold. What record of the last five years was more interesting?

Tweedy, I think, is not taking any of this for granted, and Wilco is still happily surprised to be on this big stage. So they pulled out all the stops. They played a lot of songs from “Yankee Hotel Foxtrot,” and they played a fantastic, heavy version of “Kingpin” from their second album (one of the best songs Tweedy has ever written). They played their new stuff like the world was going to end in five minutes. Every song was like an encore.

Wilco didn’t take a break – except to pass out hugs at midnight – and they pushed themselves from the moment they took the stage to blow the crowd away. Even slower songs, of which only a couple were played, were infused with a scorching, guitar drenched, rock ‘n’ roll vibe.

The Flaming Lips had gotten everyone warmed up with their insane, inviting, charismatic trip fest. The flashlights, the balloons, the pasties-and-thigh-high girls shaking it on stage. They were a charismatic romp, a great show in themselves, and a perfect set-up for the six self-effacing guys playing the hell out of their instruments.

I had the weirdest feeling at this concert. I turned away from the stage, looked at all the people with their hands in the air, all rocking out. And I felt proud of the band down the street – not settling for anything, not used to it, not inured to their own fame. They weren’t taking the audience for granted, or assuming that they’d have another chance if they blew this show. They played their hearts out.