Hard to believe, but pop singer-composer Neil Sedaka is marking 50 years of hit songs this year.

"I'm very proud to be part of the history of American rock 'n' roll," said Sedaka, 66, by phone from Los Angeles. "I've had a very diversified career, singing, writing, performing. I've always tried to vary it, make it fresh, make it stylish. My work has taken me to different places, different styles, different kinds of music."

Sedaka, who performs a pair of concerts Sunday at the Hawai'i Theatre in Downtown Honolulu, also is a survivor who knows how to reinvent himself as musical tastes change. And he's on the verge of doing it again, albeit from a grandpa's perspective.

"You have to, to stay alive," he said of his ability to adapt as the pop rock scene changes. He started in the biz as a teen, as a member of a Brooklyn doo-wop group, and was one of the early rock luminaries in a 1958 show at the now-long-gone Civic Auditorium on South King Street. Just last month, he marked his 50th anniversary with a Lincoln Center bash that assembled the Captain & Tennille, Clay Aiken, Connie Francis, Natalie Cole, Dion, Paul Shaffer and David Foster.

While the biz has radically changed, from buying actual recordings to downloading on the Web, the nature of what marks a hit hasn't: audience response.

"A hit song is always a hit song — if it appeals to the masses," he said. "The market now is (via) the Internet ... It has hurt a lot of record sales."

So he monitors Nielsen's SoundScan, which tracks sales, and markets via QVC, the shopping site, and relies on television shows such as "The View," the "Today" show and Fox News to promote his music.

"From 1958 to '63, records had a certain style. From 1975 to '80, another era of change happened. To survive, you have to have different projects, different styles. You have to change," said Sedaka, who didn't let phenoms like the British invasion, disco and other trendy motifs affect his livelihood.

He first recorded one of his signature songs, "Breaking Up Is Hard to Do," as a rock song in 1962 on RCA to suit the tempo of the times. In 1975, when he was signed to Elton John's Rocket Records label, he re-recorded the song as a ballad, and it placed him back on the charts again.

"And I'm still reinventing my music, this time with changed words, as original hits for children," said the grandpa of three.

"The new version is called 'Waking Up Is Hard to Do,' and I've done new lyrics for my other hits, like 'Where the Toys Are' (replacing 'Boys') and 'Lunch Will Keep Us Together' (subbing 'Love')."

The venture is pegged to a proposed "Papa Neil's Penthouse," being shopped to a kid-friendly cable TV channel.

For Sedaka, it's a natural progression to dabble in lyrics,

He originally wrote melodies, while his word-merchant partner, Howard Greenfield, provided the lyrics. The tunes often reflected his personal life.

"For the first few years, they put words in my mouth; for the past 25 years, the songs have been more meaningful, when you write your own music and lyrics. And yes, many personal songs do come from personal experiences," he said.

"Oh! Carol" has been widely interpreted as a love song about his high school sweetie, singer-composer Carole King. "The Diary" is a result of his failed attempt to read singer Connie Francis' diary.

Of all the songs that he's written and performed, he takes a bit of shine to "Laughter in the Rain" because "it was the comeback song, thanks to Elton John, who put me on his record label."

Sedaka said he usually writes music at the piano, "but I'll write a poem on a napkin, sometimes, then write a tune to the poem. I'll include some new songs in my concerts in Hawai'i."

It's likely his granddaughters will join him on stage at the Hawai'i Theatre; and mood willing, they'll sing, too. The Island concerts are becoming part of the Sedaka family outings every December.

Retirement is not yet part of his vocabulary. "You know, once you're in front of the people, the adrenaline rush is special," he said. "And when you get a standing ovation, you never get over it. Besides, I do 35 concerts a year; music keeps me young."

So what else is on the horizon?

"A one-man show, in June, on Broadway," Sedaka said. "It's myself, piano, DVDs — and telling stories. I did it once at Albert Hall in London. Now I want to do it again.

"Reaching people's emotions is the biggest thrill of my career. Hopefully, the songs will outlive me. When you're dealing with music, it's total enjoyment — it's not politics, it's not lecturing. I always look for something new to do, instead of relying on the old. I think that's why I've lasted so long. I try to develop and grow. And my voice is unique, recognizable. I get into a taxi cab, and the cabbie will tell me, 'It's Neil Sedaka,' without looking at me."

Reach Wayne Harada at wharada@honoluluadvertiser.com.