During the 13 months that Taylor Swift canvassed the globe on her 2011-12 "Speak Now" tour, she was joined onstage by a steady parade of celeb musician friends and admirers: Nicki Minaj and Justin Bieber in L.A., Usher in Atlanta, Brooks & Dunn's Ronnie Dunn in her home base of Nashville, Selena Gomez and James Taylor at Madison Square Garden in New York.

On the surface, the guest appearances were simply a bonus for fans — a little something to generate extra sparks, Twitter and water cooler buzz about those shows.

But the move seems to have had an unanticipated side effect on the star — and her new album, "Red."

"I reached a moment in making this album where I just wanted to get into the studio with people who do things differently than I do and see how they do it," said Swift, 22, during a recent break in rehearsals in North Hollywood. "It was really more of an experience decision. I really never want to get stuck making the same album more than once."

"Red," Swift's fourth album, is an unapologetically big pop record that opens new sonic vistas for her thanks to collaborations with pop-world heavyweights including Max Martin and his frequent songwriting and production partner Shellback, Ed Sheeran, Jeff Bhasker and Semisonic singer Dan Wilson. "Red" will be released worldwide Monday.

The new alliances manifest in the big-beat pop chorus of the album's first single, "We Are Never, Ever Getting Back Together," which she wrote with Martin and Shellback, who produced it. The title track, her essay on a best-of-times, worst-of-times relationship, opens over a simple banjo accompaniment but quickly kicks into rock overdrive with pounding drums and a throbbing bass line. The song "22" applies a strong dose of Auto-Tune to mechanize her vocal over what sounds like programmed electronic drums. And she's gained considerable attention for the peppery syncopated rhythms in "I Knew You Were Trouble," and the hints of dubstep she, Martin and Shellback weaved into her tale of yet another star-cross'd romance.

With only the most fleeting traces of the country music with which she launched her career, the album creatively too takes her deeper into the pop world than "Speak Now," for which she proudly wrote all 14 songs single-handedly. It became the first album in more than 51/2 years to sell more than 1 million copies in its first week of release when it came out two years ago. It has since sold more than 4 million copies in the U.S., according to Nielsen SoundScan.

On the floor of the rehearsal studio, Swift displays the same fire in the belly and intense drive she exhibited at 17, shortly after the release of her 2006 debut album, "Taylor Swift." But there's a new authority in her voice, perhaps culled from her transition over the last half decade from a wide-eyed ingenue to one of the biggest pop stars of the new millennium.

More obvious to the outside world than all of that is the increasingly sophisticated — and refined — fashion sense she's developed as a top-rank model and cover girl. During the rehearsal she wore a casual knit long-sleeve sweater mini-dress with black and horizontal white pinstripes, tan and brown stylized saddle shoes. The delicate gold chain around her left wrist was offset by girlish, turquoise blue nail polish. Her once curly blond hair was straight and pulled into an efficient, unfussy ponytail. The bangs scattered across her forehead framed her delicate blue eyes.

PHOTOS: Celebrity portraits by The Times

"One of the things I'm proudest of is that I feel like every one of the three albums I've put out so far stand alone in one way or another," she said, sitting on a couch in a small room off the rehearsal hall. She'd been working with her seven-piece band and half a dozen dancers ahead of their VMA show performance of "We Are Never, Ever ...," which that recently brought Swift her first No. 1 hit on the Billboard 100 pop singles chart.

"This album does that too," she said. "The reason being that, with 'Speak Now,' it was really important for me to write every song on it myself.... And for this album, it was really important for me to collaborate."

"I think the 24 guests she had on the 'Speak Now' tour really opened her mind to a lot of things," said Scott Borchetta, head of Big Machine Records, the fledgling label he launched in 2006 and turned into one of the music business' rare 21st century success stories largely on the shoulders of a 15-year-old singer-songwriter he had signed named Taylor Swift. "It really opened her mind musically and sonically."

Swift may be two months shy of 23, but she's spent half her life writing songs, and the last eight of those doing it professionally, having landed a songwriting contract with Sony/ATV Music when she was just 14. With "Speak Now," she set a record for the most songs by one artist to debut in the Billboard 100 pop singles chart in the same week: 10, all of which she wrote herself. She was just 20 when she was honored for her songwriting by the American Society of Composers, Authors and Publishers, the publishing rights organization, with its Hal David Starlight Award.

Despite all the attention on the six collaborative tracks on "Red," including the single, 10 remain Swift solo compositions. Thematically, "We Are Never, Ever…," "Trouble," "Treacherous" and "Everything Has Changed" are aligned with the songs about misfiring romances that she's been writing since she was a doe-eyed teenager desperately seeking a happily-ever-after story ending.

In "Holy Ground" and "Begin Again," however, she's exploring the more nuanced relationship issues she's encountering as an adult: in the former, recognizing her vulnerability when she's not the one being pursued ("for the first time I had something to lose"); in the latter, she looks back with clarity on the value of a fling that didn't work out, coming to the realization that it's OK to be alone.

"Everything Has Changed," which she and her duet partner Sheeran co-wrote—while sitting on a trampoline in the backyard of her house in L.A., she noted—conveys the swept-away feeling of young love, and likely will lead to speculation that it's about her current relationship with Kennedy clan scion Conor Kennedy. A more likely candidate is "Starlight," in which Swift, who still considers Nashville her home base, sings of her 17-year-old date and telling "how we snuck into a yacht club party pretending to be a duchess and a prince." It's another rock ballad with an insistent Coldplay-inspired pulse.

"For me, when people make speculations, I hope that they're making speculations because they read the lyrics," she said. "I really want people to read lyrics; I want people to care about lyrics. I think it's important that a song is more than just a thing you can tap your foot to in the car or dance to in a club. So if them speculating about who the song is about means they're reading my lyrics, it's less of an irritating thing."

Because she scored her first hit record — the savvy, country-superstar-name-checking single "Tim McGraw" — and a platinum-selling debut album while she was in high school, Swift has foregone a formal college education.

But there are the real-life credits she's earned from creating a debut album that's sold more than 5.2 million copies, and its successor, "Fearless," the biggest-selling album of 2008 in any genre, which has racked up sales of more than 6.6 million copies in the U.S.

In that sense, "Red" may constitute her master's thesis in pop music production, because she has worked and studied intensely, one on one, with experts in the field.

"I wanted to know how Jeff Bhasker makes those drum sounds," she said, fixing her eyes intently on a visitor while describing her thought process that kicked in after she'd been working for about a year on the follow-up to "Speak Now," initially once again just using her own songs. "I wanted to watch Max Martin conceptualize a pre-chorus that gets stuck in your head as much as the chorus. I wanted to see him suggest a post-hook, or a bridge that sounds like another chorus. I wanted to see how all that unfolds.... I loved watching everybody have their own process. I think moving forward that just gives me more colors to paint with."

This is the same voracious thirst for knowledge she exhibited early on, and that persuaded her parents, Scott and Andrea Swift, to move from Wyomissing, Pa., to Nashville with their ambitious 14-year-old daughter and her younger brother, Austin, who's now enrolled at Vanderbilt University in the country music capital.

Consequently, her aim on "Red" was to genuinely collaborate rather than simply add musical window dressing to what she'd been doing all along.

Case in point: "We Are Never Ever Getting Back Together" reaching No. 1, for two weeks, on the Billboard 100 pop chart, one of the few commercial peaks she hadn't yet conquered. It's also become a bona-fide hit in England, a sign of the solidifying international appeal she's been building for several years, a rarity for Nashville-based musicians.

Meanwhile, Swift continues to be a lightning rod for attention, positive and negative. For every award she collects, such as her six Grammys including the album of the year for "Fearless" and multiple entertainer of the year accolades from the Country Music Assn. and the Academy of Country Music, she weathers withering blows from listeners and music critics who dis her vocal abilities, even her enthusiasm whenever good news comes her way.

"I never have the moment where I feel like it's too much," she said. "But there's definitely the moment where I get sad that I feel like sometimes people don't believe in anything being genuine anymore. That no matter what, there's someone questioning everything that I say or do."

She makes no apologies for her pursuit of happiness or for her ubiquitous and oft-criticized expressions of wide-eyed, opened-mouth surprise each time she is on the receiving end of an award.

"The No. 1 piece of advice other artists have given me," she said, "is 'Live in the moment. Really, really understand that this is amazing.' Some of them have said, 'I let it pass me by; I didn't realize how great it was till after. And I acted really cool when it was all happening, and then afterward I realized I'd let it pass by.'

"If you really take that advice to heart, you freak out when you win an award. If you're really living in the moment, you're not bored that you won an award. I got a Grammy this year, and I really tried hard not to be as excited — not to act so excited when I won. But," she said, breaking into laughter, "I get so excited and I just was; I was really, really happy about it."

randy.lewis@latimes.com