AT A MIDWINTER show in the cozy confines of SE Clinton Street’s Press Club, Rachel Taylor Brown holds the room rapt, her auburn locks falling over the keyboard as she sings. Her bearded bandmates chime in with lower vocals—but a mysterious high note hangs almost imperceptibly in the still, dark air. Ears perk, heads turn, and several eyes finally find the source: another redhead sits at the back of the room, evenly, effortlessly suspending the ghostly tone.

Arts insiders might recognize the harmonist as Katie Taylor, a veteran of the quirky Opera Theater Oregon (OTO) who was recently promoted to producing artistic director. But to the lead vocalist, it’s just her kid sister. A few weeks later, over Sunday brunch, they display another version of siblinghood, punctuating each other’s stories with effortless entwining of hands and testimonies of support. And as Katie pitches in with backing vocals, the sisters will commit a little of their family bond to an album (Rachel’s seventh), World So Sweet, set for a May release.

Their duet hasn’t always taken the form of song. As the youngest kids in a seven-sibling family from Boring, the sisters faced their brother Jeff’s untimely death from brain cancer, and as adults stood shoulder to shoulder through revelations of childhood abuse. But through much of their nearly four decades together, they also have made music.

Rachel’s piano-and-vox-driven songs still hint at the long-lapsed dramas of their youth, with elements that are at turns tense, tragic, and gorgeously embellished with religious and literary imagery—and yet somehow still catchy. Her classical-yet-edgy sensibilities on albums like Susan Storm’s Ugly Sister (2009) and Ormolu (2006) have earned accolades from NPR, even as they receive frequent nods from niche fan blogs like Absolute Punk, which calls her music “daring, fearless and chilling”—no small compliment from the punk-rock camp.

“Rachel is one of the most artistic people I’ve ever worked with,” says producer and engineer Jeff Stuart Saltzman, who has also worked with Stephen Malkmus, Death Cab for Cutie, and the Decemberists, and has long been Rachel’s go-to engineer. “Her process can be very playful and painterly, but when she sits down to write a group of songs, she’s very certain. Sometimes her expectations of what I can do as an engineer are way outside of what I think I can do, but then she ends up pushing me, and I go, ‘Wow. I guess we can do that.’”

When Rachel gets Katie and OTO in the mix, the results can be downright dazzling. The opening of World So Sweet features 50 pianos and as many singers (including Katie) performing the title words in luxurious choral harmonies. Major thirds resound and overtones abound. “It’s pretty powerful, pretty huge-sounding,” Saltzman says. “And when just Katie and Rachel sing together, too, their voices are so complementary, there’s a kind of stereo effect.”

As Rachel and her producer fine-tune the new album, blending in instrumental takes from pro Portland players like Menomena’s Justin Harris and Danny Seim, she will also be indulging her more Byzantine leanings by singing soprano with vocal chamber ensemble Cappella Romana on April 2 and 3. She faces this performance, modern minimalist composer Ivan Moody’s Akathistos Hymn, with awe and slight trepidation: “You’re camped out on, say, a high A, just droning that, while someone else is doing some ornamental thing in between. It’s a really cool piece—but the breathing is brutal.”

Meanwhile, Katie is moving into her sixth year at OTO with great strides, having secured a new home for the company after their effort to refurbish the Guild Theatre fell through last year. (Having read of OTO’s plight, local beer-magnate Mike McMenamin offered an office in the Mission Theater.) Now, with ship righted and helmswoman set, the kitschiest opera outfit in town can sail into ever wilder winds with more productions like Hercules vs. Vampires, a collaboration with cult-movie exhumers Filmusik that adds a live opera score to a vintage Greco-Roman-themed thriller. In May, OTO will again team up with Filmusik to reprise an ’09 rendition of Rudolph Valentino’s 1922 silent film Camille, paired with live music from Verdi’s opera La Traviata.

But as the two sisters look forward to their upcoming performance together for the release of World So Sweet, the stories they tell are mostly about each other. “I’ve known her long enough now that I tend to take all of her obvious perfections for granted,” says Katie, touting her sister’s talents for melody, universality, arrangement, and empathy. “In some ways, I wish she had gotten to be a boy, so people would let her be Elliott Smith, or Leonard Cohen, or John Lennon. That’s the kind of reputation she deserves.”

“No, Katie should get to be the queen of her own small nation,” Rachel deflects. “And I will move there and be the Billy Carter, just hanging around with a beer, and embarrassing her as hard as I can.”