A real surfer never gives up a secret surf spot. Not even to highlight his own Cinderella story.

When Waimanalo-raised Kenneth "Boom" Gaspar chats about the day four years ago when Eddie Vedder asked him to join Pearl Jam, he happily explains how they struck up their friendship.

Where they struck up that friendship, however, is another story.

Kane'ohe resident Gaspar has been Pearl Jam's keyboardist and unofficial sixth member since 2002. He's played on two of its albums — 2002's "Riot Act" and 2006's "Pearl Jam" — and toured with the Seattle-based band worldwide every year since.

An invitation to accept a new position in a superstar band that has taken on new members only when one of its five core members has exited would've been accomplishment enough for any musician. Factor in that Gaspar, when asked, was 49 and a gifted but mostly unheralded veteran of the Hawai'i music scene who didn't even know who Pearl Jam was and that makes it close to miraculous.

Now 53, Gaspar's keyboard time at Blaisdell Arena on Saturday night will mark the first time he's performed live with Pearl Jam in his hometown. After keeping his job mostly on the down-low here, the low-key Gaspar seemed excited to finally discuss how he wound up in Pearl Jam.

Gaspar was introduced to vocalist and part-time Hawai'i resident Vedder by a mutual friend while riding waves at that aforementioned surf spot.

"I thought he was a swell guy," said Gaspar, his sandpapery voice a warm and mellow pidgin-rich purr. "We kept acquainted from time to time at the surf spot and enjoyed each other's company."

All that mattered was that the other was "cool." Personal lives were not discussed.

"I knew him as my friend Eddie. I didn't know how big he was. I just loved him for how he was ... and how he came off to us."

Nine months passed before Gaspar found out Vedder, like him, was a musician. Gaspar asked the band's name.

"He said, 'Oh, a Seattle band. We're just kicking it around,' " Gaspar said. "I didn't want to get niele (translation: nosy), but I asked for the name."

Pearl Jam, said Vedder.

"Who's that?" Gaspar queried, genuinely unaware of who or what Pearl Jam was. The very private Vedder cracked up.

"He had a big smile on his face because he knew I had no inkling about his life (or) who he was."

Vedder, however, knew who Gaspar was, having seen him work magic on a Hammond B3 organ. Gaspar had played keyboards since age 9, instructing himself in pop, jazz, soul and funk styles by emulating keyboardists like Stevie Wonder, Ray Charles and Santana's Gregg Rolie.

A Kailua High grad, Gaspar spent much of the next 30 years eking out a living mostly as a background player for musicians such as Henry Kapono and Bruddah Waltah. Bands included Harmony in the mid-'70s and Simplicity in the late-'80s.

"If I wasn't playing, I was working odd jobs to survive. If I wasn't playing, I wasn't making any money," said Gaspar, chuckling. "So I tried to stay as active as I could. Even if I had to put bands together and look for gigs. Anything to survive."

One night, near their surf spot, he and Vedder started jamming.

"He had a guitar. I had a keyboard. It was a small set-up. And we wrote," said Gaspar.

That would be the song "Love Boat Captain."

When they were done, Vedder looked at Gaspar and asked, "Are you ready to go to Seattle?" Gaspar requested Vedder ask his wife, Pinky, if it would be OK. Fortunately, she approved.

Gaspar jelled so well with the band on "Love Boat Captain," he was asked to add keyboard parts to the rest of Pearl Jam's "Riot Act" CD. Back home post-recording, he got a call from Vedder.

"He told me, 'All the boys had a meeting and decided that we want to take you on tour with us,'" said Gaspar. "I lost it. I was yelling. I was jumping. My house was shaking. I was so happy."

Gaspar still doesn't know what they saw in him, but feels blessed they saw something.

"This is just a job that God blessed me with. It's all from Akua," said Gaspar. "I always wanted to make it musically. ... And I told God that if I made it, I'd turn around and help give back to my community."

With Saturday's show, he will. At the Gaspars' request, Pearl Jam's nonprofit Vitalogy Foundation will donate a dollar per ticket to Hui Malama o ke Kai, an after-school, ocean-based program for Waimanalo youths.

"I came from the streets of Waimanalo ... My father built a shack for us when we were kids to play music and to have a place to hang that wasn't in the streets," said Gaspar. "We didn't have youth programs or after school programs so a lot of my friends got lost in the shuffle.

"Hui Malama takes kids to the ocean to learn about the ocean. We picked Hui Malama because (they're) Waimanalo. Like me."

Reach Derek Paiva at dpaiva@honoluluadvertiser.com.