NEW YORK—Solange Knowles turns out to be a little sensitive about using a certain b-word.

No, not that b-word.

This b-word: Beyonce.

Solange, 22, is reluctant to discuss her older sister—the Bootylicious One—and it’s understandable why: All anyone seems to want to know is about their relationship, and yet one of them is still trying to make a name for herself.

“I’ve answered that question and then that’ll be the one thing from a 40-minute interview that gets any play. That is what becomes frustrating,” she says. “It’s a little repetitive.”

Sorry, Solange.

The good news is that she has something of her own to crow about: “SoL-AngeL and the Hadley St. Dreams,” a sophomore album that’s anything but sophomoric.

The 13-song CD starts with a blast of 1960s-inspired R&B—think The Marvelettes and The Supremes—before evolving into more downbeat electronica.

“This is exactly what I wanted my record to sound like, from top to bottom. This is exactly where I was musically when I recorded it. My influences, my inspiration, my honesty is poured into this record,” she says.

There’s the foot-stomping “T.O.N.Y.,” the American Bandstand-sounding first single “I Decided,” the hip-swiveling “Sandcastle Disco” and the Gaye-inspired “Ode to Marvin.” There’s also a smoky duet with Bilal.

Big sis—that dreaded b-word—does get a mention, albeit obliquely. “I’m not her and never will be,” Solange sings on “God Given Name,” the opening track. “Two girls going in different directions/Striving towards the same galaxy/Let my star light shine on its own.”

“What I love about Solange is she dares to be different,” says her father, Matthew Knowles, an executive producer on the album. “I think people are finally getting it—that she is different from her sister. And that’s OK.”

There’s little doubt that Solange’s star shines differently. While her sister appears more poised and proper, little sis is raw and outspoken. She has tattoos, she curses and she’s prone to rashness. Her publicist seems perpetually skittish.

During an interview in her label’s office, a tired Solange collapses on a leather sofa and never gets up, transforming into a horizontal diva with huge hair, impossibly high heels and what looks like a mini-prom dress. The whirlwind promotional tour has sapped her strength.

Five years younger than her sister, Solange has already amassed quite a musical history. She joined big sis on a Destiny’s Child tour as a dancer and helped write such songs as “Upgrade U” and “Get Me Bodied” for Beyonce, and others for Destiny Child alums Kelly Rowland and Michelle Williams.

Though her new disc is technically her second album, Solange is pulling a Joss Stone—declaring her second CD the real debut and distancing herself from the first.

That album, “Solo Star,” came out in 2003 and sold some 112,000 copies. Though it reached No. 23 on Billboard’s Top R&B/Hip-Hop Albums chart, critics found it too muddled, veering awkwardly from reggae to hip-hop to pop.

Solange took time off after that, marrying Daniel Smith, her childhood sweetheart, at 17; giving birth to a son, Daniel Julez; and moving to Moscow, Idaho, while Smith attended college. Now divorced, she and her son have made their home in a loft on Hollywood Boulevard.

“It’s definitely a sense of balancing and I feel like I do it well,” she says about single motherhood. “The key for me is really to learn when to say no.”