Kids screamed. At least one cried. Others were so excited they forgot to play notes on their 'ukulele.

That pandemonium occurred yesterday at the Kapi'olani Park Bandstand when Grammy-nominated musician and North Shore resident Jack Johnson surprised young musicians by joining them on stage. He became one of about 480 people who played together during the Starbucks 37th Annual 'Ukulele Festival in an effort to set a Guinness world record for most 'ukulele playing a single song.

The about 400 children on stage had practiced one of Johnson's songs, "Breakdown," having been told they'd be part of the record-setting attempt. Having Johnson stroll onto the stage was icing on the cake. About 80 adults also crowded onto the stage and bandstand stairs to play the song.

"When I saw him, I was kind of freaking," said Rianne Kawano, 11, who was joined on stage by her mother, Kathy, and stepsister, Elissa Wong. "I was kind of like screaming inside."

Others beamed at being able to share a musical experience with Johnson, freshly back in the state from Australia, where he played in a Live Earth concert. Several months ago, he committed to appear as one of the unpaid entertainers at the event organized by longtime Hawai'i 'ukulele teacher Roy Sakuma and his wife, Kathy. The free concert showcases the talent of many of the state's top 'ukulele artists along with providing a stage for hundreds of children who play the four-stringed instrument.

Johnson, wearing a green Sunset Elementary School T-shirt, corduroy shorts and slippers, said he was attracted by the chance to play with the kids. After completing "Breakdown," Johnson remained on the bandstand, turned to the kids and taught them several chords so they could accompany him on another of his songs, "Bubble Toes."

A crowd of at least 6,000 responded enthusiastically to Johnson, who played four songs and sat in on another group's performance.

"Hearing kids play music, to me, is just kind of the complete expression of joy coming out," said Johnson afterward.

"It goes two ways — to be here and inspire the kids a little bit. But they definitely inspire me. It just kind of reminds me why you play music."

Johnson said he first picked up an 'ukulele when he attended kindergarten and later received an old Kamaka 'ukulele made of koa from his parents after he began playing the guitar at age 14. He still has the Kamaka.

Johnson wasn't aware the performance was being submitted to Guinness, the U.K.-based publisher of a world records book, though he said he had always wanted to be listed there. Sakuma said a letter has been sent to Guinness informing them of the effort and that an exact number of players will be tallied from photographs and video.

The group included many of Sakuma's own students along with more than 100 people from Japan, elders from California, folks who traveled from Hilo, and Simon Clothier, an entertainer who came from London. The youngest player was 7. The oldest probably were in their late 70s, Sakuma said.

"It was like a family thing, with different places performing," said Sakuma, who also noticed eyes grow large and kids screaming when Johnson came to the stage.

"I thought this is so cool being on the stage with Jack Johnson," said Rianne's sister, Elissa. The sisters' friend, Tiffany Miller, also got excited. She has Johnson's songs on her iPod and counts herself among his fans. But Tiffany, 11, said the performance wasn't her best.

"I wasn't really looking at my fingers. I was looking at Jack Johnson behind me."

Reach Greg Wiles at gwiles@honoluluadvertiser.com.