It’s hard to believe that 15 years have passed since Backstreet Boys redefined the modern musical landscape, ushering in a chapter of pop culture that commandeered the world’s radio airwaves, broke music and concert sales records, and launched a new generation of teen idols for millions of youth. You were there: Remember the cool, silken harmonies, the passion-fueled mania that followed their every move? Perhaps you even had a BSB poster on your wall. In all, the group has sold more than 75 million albums worldwide. Their first two U.S. releases both received the Diamond Award for sales of more than 10 million: “Backstreet Boys” in 1997 and quintessential “Millennium” in 1999, which reached No. 1 in 25 countries. They have scored a dozen top 40 hits, including top 5 smashes “Quit Playing Games (with My Heart),” “As Long As You Love Me,” Everybody (Backstreet’s Back)” and “All I Have To Give.” A lot has changed since 1997, when we first got to know the five singers comprising Backstreet Boys: Nick Carter, Howie Dorough, Brian Littrell, AJ McLean and Kevin Richardson. Today, like their fans, they have grown up and started families, recorded solo projects, and appeared on the Broadway stage, all while dealing with the trials and tribulations that accompany fame at an early age, including substance abuse, management snafus and even major health issues. Also notably, in 2006, Richardson amicably decided to exit the group, with the full blessing of his teammates. But as we hear on their sixth album, “Unbreakable,” due Oct. 30 on Jive Records, what remains gloriously synonymous are BSB’s indelible melodies, hooks galore and finely crafted three- and four-part harmonics, demonstrating that these guys have matured into talented musicians who still love what it is they do so well. “To still be around feels amazing,” says Howie. “So many artists, boy bands and rappers that started when we did have disbanded. We look at artists like the Eagles, the Rolling Stones or Aerosmith, where everyone has done individual things, but they are still able to come back together. I admire that kind of staying power.” Adds Brian, “The pop bands of yesteryear that don’t exist anymore were centered around one or two central vocalists. What has allowed us to keep going is that we were always a team of well-rounded singers, with a similar vision. We’ve been through so much together, on equal terms, and that either tears you apart or brings you closer. When we took a break from 2002 to 2005, it was such a blessing to step outside of our own spotlight and focus on the value of something other than being a pop star. We needed to go through that character building in order to maintain respect for what we all have as a group.” Backstreet Boys spent a year and a half recording “Unbreakable,” which marks a confident return to the pop template that best defines the group’s sound. First single “Inconsolable,” produced by Emanuel Kiriakou (Nick Lachey, Celine Dion, Katharine McPhee), is a classic piano-driven midtempo ballad reminiscent of the group’s biggest hits. Upon its release in September 2007, it was an instant add at pop radio stations across the country. All 13 tracks on the set, in fact, demonstrate an organic ease with material that is an ideal fit. “Helpless When She Smiles” is another stunning hit-worthy midtempo ballad, produced by Grammy-winning John Shanks (Kelly Clarkson, Sheryl Crow, Bon Jovi, Hilary Duff). A number of other tracks were produced and co-written in Nashville by Dan Muckala, who worked with Backstreet Boys on previous album “Never Gone.” Among his standouts is the moody Beatles-esque “Unsuspecting Sunday Afternoon”—a song that all four singers herald as a highlight of the set. BSB asked heralded songwriter Billy Mann to collaborate on the song with Muckala. The result, says Brian, “is a love story, but with an unexpected message that really makes you think. Melodically, the bridge becomes another song, which I love. It’s really all about the emotion of the vocals, and it’s different than any other track we’ve recorded.” The boys met Muckala five years ago, when he was writing for a number of Christian artists. “He was sort of trapped in that category and we could tell he was ready to blossom into the secular world,” Howie says. “We were lucky to catch him at that stage, and he really inspired us with ‘Incomplete,’” the first single from “Never Gone.” “Sometimes people have that huge hit and their rates triple and they lose their humility. But Dan remains humble and we were all eager to work together again.” Also among priorities this time around, BSB wanted to include enough uptempo tracks on the new album to showcase in their trademark kinetic live shows. Synthesizer-soaked “Everything But Mine,” playfully frenetic “Panic,” galloping “Any Other Way” and creepy crawler “One in a Million” ably fit the bill. On “Never Gone,” the group experimented with a more guitar-fueled motif, which ultimately left them longing for the classic dance tracks that have traditionally accompanied their onstage performances. “The rock sound limited us from doing as much choreography,” Howie says. “When we were in the studio, we recorded more than 30 songs, but made the conscious decision that this album should return to that middle ground, so our fans realize we haven’t lost touch with who we have always been. Performance is such an important element of the Backstreet Boys.” “We can’t wait to get back onstage and put a big extravagant show together using this material as the base,” adds Nick. “Half of what we do is vocals and harmonies on our albums, but our other role is entertainers, which we take pride in.” AJ notes with a laugh, “We don’t want to be a bunch of geriatric boys sitting on stools when we perform. I think when you hear the record, you can see how much fun these songs are going to be to perform live.” While it would be clever enough to declare that “Backstreet’s Back”—hearkening the title of their hit song—the truth is they never went away. Over the course of 15 years, they maintain rare relevance in an industry that so often disposes of pop acts with ultimate haste. “We love the fact that we can still lift people’s spirits and make them smile with songs they can sing along to. I do think we’ve found a magical sound,” Brian says. “We’ve grown up together with our fans for this long. Hopefully, we can stay together for another 15 years.” “Our music has evolved with our fans. We were young pups when we started,” adds Howie. “With each album we’ve had the opportunity to grow more mature, lyrically and vocally. We’ve also had the chance to educate ourselves about the business, about artistry and becoming real musicians. I hope that shows with each step we’ve taken.” And, notes AJ, “We’ve been part of this group for half our lives—it’s crazy to think about. If you asked me in 1992 if I’d still be a Backstreet Boy in 2008, I’d have thought we’ll make some records together and have a good little run. But we continue because we love what we do. We thrive being onstage and seeing the faces of little girls and boys and couples and grandmothers, all cutting a jig in the front row. If we were to write a book based on our experiences, I think it would be longer than ‘War and Peace.’ When I’m a grandpa, I’m going to have a lot of stories to tell.”