A lot of things have changed since Emilio Castillo and the other founding members of Tower of Power got together in Oakland, Calif., in 1968. One of the biggest changes for them in recent years has been the double whammy of iPhones and YouTube.

“We used to work up new material, take it out on the road, try it out with the audience,” Castillo said, in a May 3 phone call from the Bay Area, where he was visiting his father. “It would grow and morph, and then we’d go record it. That was a great process. But now, if I play a new song onstage, on the way back to the hotel it’s on YouTube. I’m not griping about that; it’s the way it is.”

“The way it is” assays out as a “bad thing, good thing” for Tower of Power fans here who are anticipating the group’s return to the Blaisdell Arena on Saturday. The “bad thing” is that there won’t be any works in progress on the set list. The “good thing” is that this leaves more time for Hawaii to enjoy more of the group’s early hits and coulda-been-hits from the 1970s. In Hawaii that is a very long list.

Tower of Power hit so big in Hawaii in 1972 with second album “Bump City” that Waikiki club bands like the Dimensions played almost every song, and those on the next one, 1973’s “Tower of Power,” as well.

Four decades later Hawaii fans come primed for the hit singles — “You’re Still a Young Man,” “Down to the Nightclub” and “So Very Hard to Go” — and album tracks like “You’ve Got to Funkifize,” “You Strike My Main Nerve,” “Clean Slate,” “Don’t Change Horses (in the Middle of a Stream)” and “Squib Cakes.” Memories, memories!

Castillo, 65, says it’s great to meet young fans who tell him they learned about Tower of Power from their parents or grandparents. He credits music teachers and high school band programs with also introducing the music to new generations.

“A lot of music teachers throughout the world now are saying to these kids, ‘Check this out,’” Castillo said. “If you had your choice of playing a John Philip Sousa march or ‘Squib Cakes’ — which kicks a little harder — which would you choose?”

He never figured the band would have such longevity. “I just had a passion to do this,” he said. “Before you know it, somebody’s telling you, ‘You’re an institution, man, you’ve been together 20 years.’ Then you’re a legend, you’ve been together 30 years. At 40 years they start running out of adjectives. Now we’re closing in on the 50-year mark. It’s just amazing.”

Among the building blocks of that success are the consistently powerful arrangements of the five-man horn section. Another is things that Castillo and Stephen “Doc” Kupka write about.

Castillo was coming from the heart when he and Kupka wrote the song that would become their first hit, “You’re Still a Young Man.” Castillo was 18, and a 24-year-old woman had told him that he was too young for her.

“I doubt that I would have written that first song if it hadn’t been for Doc,” he said.

For the first couple of years, Tower of Power played other artists’ material, but they didn’t play other artists’ hits. “We’d take the obscure tracks off the albums, and I would put a different rhythm to it and change the background and make up some different horn parts. (Doc) came to me and said, ‘What you’re doing with these songs, it’s amazing, but why are we doing it to other people’s songs?’”

Age issues — someone being “too young” or “too old” for someone else — are as relevant today as they were 40 years ago.

Or consider “What Is Hip?” — a catchy piece of piece of social commentary they co-wrote with drummer David Garibaldi in 1973. As the song says, “doing a hip trip may be hipper than hip,” and it is also true that “what’s hip today might become passe.” Those facts of life have defined the lives of fashion mavens and fad-chasers for decades.

The biggest change since Tower of Power was here in 2013 is that Marcus Scott has replaced Ray Greene as the group’s lead vocalist. When Scott officially joined Tower of Power in April, he added his name to the list of more than 60 musicians and vocalists who have performed as members of the group since 1968.

“We lucked out and got another great one,” Castillo said of Scott. “God is really blessing us.”

“We’re in the process of recording an all-original CD,” he continued. “We’ve recorded 28 songs, trying to put together the best CD of our career ’cause we’re coming close to 50 years in the business — this August will be 48 — and we’re planning to release this record sometime in 2017. We’re gonna do a DVD documentary kind of a thing and a 50-year celebration somewhere, probably in the Bay Area.”

Going back almost to the beginning, Castillo revealed that when they recorded their obscure first album, 1970’s “East Bay Grease,” their producer told them that “You’re Still a Young Man” was “too mushy” and wouldn’t let them record it.

To record “Bump City,” the band changed labels, and went down to Memphis to work with Steve Cropper. “You’re Still a Young Man” became the first hit on the record.

Does that put their first producer in the Rock and Roll Hall of Infamy with the Decca Records executive who passed on signing the Beatles in 1962 because “guitar groups are on the way out”? Castillo says no.

“He made the decision to sign us at a time when we were nobody, so that guy took a big chance. For the times (in 1970) he was right, but two years later they were ready for it.”

Listeners remain ready to hear it now.