Wilco are the greatest live band playing today because they're the most romantic band playing today. They woo their audiences, play with them—they aren't afraid to take risks, to slide a little out of control. After a decade as a band—originally alt-country, now something else entirely—they have endured collapse and lineup changes and rehab, and are at their prime.

Two years ago, I saw the Chicago six-piece at an outdoor amphitheater in Pompano Beach, Florida. It was a drunken party, women on their boyfriends' shoulders, woo-hooing through quiet stretches of song. Jeff Tweedy seemed almost nervous at the outpouring of oblivious affection. "You better not show me your tits," he said sheepishly to one shoulder rider. "I don't know what I'd do." When a guy rushed the stage and sat down at his feet, Tweedy said, "That's weirder than if he tried to hug me." (He's not always so gentle—Tweedy famously smacked an aggressive fan who scrambled onto a Missouri stage a few years back.)

The sold-out crowd at Marymoor Park on August 21 was a total contrast—rapt and reverent, singing along at the appropriate moments, clapping on demand, cheering for solos and climaxes. The sound was pristine—it could've been louder, but a park staffer said that was the band's choice. This was a concert, not a party; it was more devotion than celebration.

Wilco started without a word. Tweedy dove gently into the intimate "Sunken Treasure," he and the crowd lingering over the line "I was maimed by rock 'n' roll." A song later, they went into "I Am Trying to Break Your Heart." Whenever, wherever I hear it, that song kills me. I was in the photo pit at the front of the stage, staring straight up into Tweedy's nostrils, camera clicking away—and still stricken. Nobody does true romance like Wilco.

Tweedy is a master of worn-in, worn-down, hoping-to-just-get-by lyrics, and he can stretch a common image into something sad and quietly dramatic. From "A Shot in the Arm": "The ashtray says we were up all night." And "I Am Trying to Break Your Heart": "Let's undress just like cross-eyed strangers." And "Jesus, Etc.": "You were right about the stars—each one is a setting sun." As he sang them, the words sounded easy, intuitive, and true.

Every great rock band has its lead and its foil; in Wilco's case, Nels Cline is the reserved, smoldering instrumentalist who counters Tweedy's diamond-in-the-rough street-corner troubadour. Throughout the night, Cline played a 12-string electric, as well as a six-string and lap-steel guitar. His solos from Sky Blue Sky seemed more eloquent live than on the record—they were longer, more expressive, and, watching him play them, they made more sense. He quietly switched tones and moods within the songs, taking his own small detours, but always heading toward that crucial moment when he fell in sync with the rest of the band.

"Via Chicago" was the peak of the set, the band at its most daring and playful. Transplants in the crowd shouted out love for their home city as Tweedy strummed an acoustic guitar, alone in the spotlight. Suddenly, the rest of the band crashed in like they had come from another song, metal to Tweedy's velvet, a different rhythm at a crazy volume, then fell back into silence. People in the crowd exchanged surprised, what-the-fuck? looks. Tweedy continued strumming like nothing had happened. Then another crashing intrusion, laughable, and this time Tweedy's quiet melody and the band's off-kilter roar aligned into manic crescendo and took the song into orbit.

During the first encore, Tweedy introduced "a friend of ours, a local guy." Seattle avant guitarist Bill Frisell emerged in jeans and fleece, looking like he'd just shut down his computer and walked over from Redmond to sit in on a couple of songs. Besides demonstrating that Wilco are friendly with respected senior musicians, he didn't add much. As self-contained as the band are, I don't think he could've.

The sky had darkened and a tilted crescent moon hovered on the left side of the stage. The night air was fresh, free from the past weekend's humidity. It was not the time to leave Marymoor Park. The crowd's only wish: a second encore.

"Spiders (Kidsmoke)," like "Via Chicago," pivoted on heightened engagement with the band and the audience. It began with a drawn-out, subdued drum pulse, Tweedy's lyrics oblique and the rhythm suggestive. The song unfolded slowly, and though we all knew what was coming, it was still a rush when it arrived: an explosion of guitar heroics, a burst in the atmosphere from devotion to celebration. Now fists pumped and woo-hoos went up. This was the feeling of falling in love, and it was mutual.recommended

jzwickel@thestranger.com