At the recent Willie Nelson tribute concert, Willie: Life & Songs of an American Outlawthe country icon was surrounded by his long-standing musical friends, most of whom he'd shared the stage with at one time or another. While that made for some great camaraderie and onstage hijinks, it also meant that there were plenty of performers on hand to offer their takes on what it's really been like sharing the stage with Nelson over the years.

For one thing, Nathaniel Rateliff explained, the legendary performer's command of the stage is just as impressive and effortless now as it always has been. "I mean, he has no setlist. He just has a clock that counts up to 60, and he just calls 'em out," Rateliff related backstage before the tribute began. "I can't even do that, so that's really impressive to me."

Derek Trucks and Susan Tedeschi, two performers with years of experience onstage with Nelson, add that this free-form approach to live shows can make for some unforgettable surprises.

"There was this one time we were playing on his 70th birthday, and he was like, 'Susan, just come on up and sing,' and I was like, 'Okay, great,'" Tedeschi recalls. "So I get up there, and I was up there with Shelby Lynne and singing background for him. He's like, 'Sue, play guitar,' so I start playing guitar, and before I know it, I'm there for, like, eight tunes and I'm just learning the tunes as I'm going."

As Tedeschi knows well, there's no telling who's going to get up on the stage, or what's going to happen, during a Nelson show.

"You never know what's going to happen! I remember that Jessica Simpson got up there and started, like, grinding on Willie. I was like, 'Oh my God, what's happening?!'" she continues. "It was hilarious, because it was his birthday, so she started singing "Happy Birthday" to him. The funniest thing about it was that everybody in the audience joined in, and then at the end, she was bummed out that everyone sang and she wanted to sing again. So she sang another verse. Who sings two verses of "Happy Birthday"?!"

Adds Trucks with a laugh, "He had his ladies that night."

Nelson's onstage antics may make it look as though he's just having fun and goofing off -- and he is. However, Trucks explains, behind that onstage party, there's a fundamental skill that allows Nelson to improvise onstage while still bringing everyone he's performing with along for the ride with no missteps.

"A lot of the tunes he wrote, they're the building blocks of what we all do," Trucks notes. "You know it innately. So when you get up and play with him, it's like he wrote the book, and we all read it. It's an amazing thing."

Everyone who's played with Nelson live has a story about thinking they were getting up for just one song, and then winding up in an onstage jam that lasted much longer. "In Jacksonville, I went to see him, and he does the same thing: He gets you up for a song and you're there for an hour," Trucks goes on to say. "It's a good way to spend a day."

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