Providing an instant answer, Willie Nelson, wearing a cowboy hat and red-white-and-blue guitar strap, slowly strolled on to the stage on his 90th birthday, bringing the crowd of more than 17,000 to its feet.

Nelson sat in a chair — one of the few onstage concessions he’s made to age — and joined Young for the rest of their 1985 duet, “Are There Any More Real Cowboys?”

“I want to thank all the artists who came out tonight to help celebrate whatever it is we’re celebrating,” said Nelson, feigning senility and getting a laugh.

The moment came three hours into the first of a two-night celebration of the country legend at the open-air Los Angeles amphitheater, where generations of stars sang his songs in tribute.

“As a kid growing up in Texas, it seemed like there was nothing bigger than Willie Nelson,” said Owen Wilson, one of the evening’s emcees along with Helen Mirren, Ethan Hawke and Jennifer Garner. “And looking out at the Hollywood Bowl tonight, it still feels like there’s nothing bigger than Willie Nelson.”

After Young, Nelson brought out George Strait, a country superstar of the following generation, for their self-referential duet, “Sing One With Willie,” followed by the Willie perennial, “Pancho and Lefty,” with Strait singing the part once played by the late Merle Haggard.

Nelson then shouted, “Come out and roll one with me Snoop!”

Strutting out came rapper Snoop Dogg, sitting next to Nelson as they launched into their stoner anthem, “Roll Me Up and Smoke Me When I Die.” Perhaps fittingly, each seemed to forget the words at times. The two friends looked too happy to care.

“Somebody make some noise for the legend Mr. Willie Nelson!” Snoop shouted mid-song.

The parade of partners illustrated one of the night’s themes: Willie brings people together.

“All of the sudden, it didn’t matter if you were a hillbilly or a hippie, everyone was a Willie Nelson fan,” Wilson said of Nelson’s late-blooming emergence as a singing superstar when he left Nashville, Tennessee, and returned to his native Texas in the 1970s. “Even the Dalai Lama is a Willie Nelson fan. It’s true.”

The crowd, which ranged from small children to seniors, illustrated the point. The stands were dotted with cowboy hats while hippies danced in the aisles and weed smoke wafted in the air.

Miranda Lambert thrilled them with a rousing, sing-along version of “Mammas Don’t Let Your Babies Grow Up to Be Cowboys,” Nelson’s 1978 hit with Waylon Jennings. The Chicks blazed through 1970’s “Bloody Mary Morning” at the same break-neck pace that Willie and his Family Band played it live in their prime.

Nelson has outlived nearly every member of that band, which backed him for decades of constant touring and recording. His little sister and piano player, Bobbie Nelson, died last year. She got her own tribute from Norah Jones, who banged the keys through the younger Nelson’s saloon-style solo song, “Down Yonder,” from Willie Nelson’s definitive 1975 album, “Red Headed Stranger.”

While many of the women who took the stage played rousing rockers, most of the men went in for quiet emotion.

Chris Stapleton kept his guitar at his side through a soft, reflective rendition of “Always on My Mind,” Nelson’s biggest solo hit of the 1980s. Nelson’s son Lukas sang “Angel Flying Too Close to The Ground” alone with his acoustic guitar, his voice a dead ringer for his dad’s.

Another surviving member of the Family Band, harmonica master Mickey Raphael, was part of the weekend’s house band, led by Don Was, which backed almost everyone.

Nelson also has outlived most of his classic collaborators. But an essential one, his 86-year-old Highwaymen bandmate Kris Kristofferson, made it to the stage to join Rosanne Cash, the daughter of another Highwayman: Johnny Cash.

Rosanne Cash was singing Nelson’s “Loving Her Was Easier (Than Anything I’ll Ever Do Again)” when Kristofferson, who wrote the song, came out and harmonized with her on the choruses.

Nelson’s musical diversity was another evening theme.

“He blends and bends genres,” Mirren said from the stage. “His timing and categories are his own.”

Leon Bridges’ “Night Life” showed off Nelson’s affinity for the blues, as did Jones’ jazzy trip through “Funny How Time Slips Away” from 1961, when Nelson was known primarily as a songwriter of hits for others.

Ziggy Marley sang “Still Is Still Moving To Me,” which Nelson recorded in 1993 and later sang with Toots and the Maytals in one of his occasional forays into reggae. Marley shouted “Wee-lay!” in his Jamaican accent during the song.

Sunday’s night show will feature a whole different range of acts including Dave Matthews, Sheryl Crow and Emmylou Harris.

Young first took the stage with his early collaborator Stephen Stills. The pair played a revved up version of “For What It’s Worth,” swapping guitar solos on the classic hit they made as members of Buffalo Springfield in 1966.

Nelson brought out all the evening’s artists to join him for the Carter Family’s 1935 song, “Will the Circle Be Unbroken?” a longtime live favorite of his and the classic closing song for all of country music.

It was clearly intended to be the end, as Hawke took the mic and started to thank everyone for coming.

But the 90-year-old wasn’t ready to stop. He interrupted and broke into Mac Davis’ “It’s Hard to Be Humble,” which Nelson and his sons recorded in 2019.

It was a funny choice for a final song, but its chorus was a perfect comic coda for a man who had been drowned in adoration all night:

“To know me is to love me, I must be a hell of a man. Oh lord, it’s hard to be humble. But I’m doing the best that I can.”