Growing up in rural Louisiana and then later on a farm in Missouri, Julianna Barwick was a preacher's daughter at a church whose organ got very little use. "We would always sing a cappella," she explained in an interview a few years ago, "And instead of instruments we would clap or sing in rhythmic rounds." A curious kid and a bit of a loner, Barwick showed a precocious fascination with the human voice. Her hobbies included harmonizing with random sounds, making up songs about whatever she was doing at the moment, and singing long, loud notes in hollowed-out spaces like parking garages and inside the trunk of a giant tree just to see what the echo would sound like. "It sounds kinda psycho, I know," she admitted in our interview, but sometimes "I would sing to myself and get so lost in it that I would cry."

Actually, it doesn’t sound that crazy; it’s very easy to become lost in the music that Barwick now makes as an adult. Over the span of her career, from her imaginative 2006 debut LP Sanguine up through 2011's dazzling breakthrough The Magic Place (the name is a nod to that aforementioned giant tree trunk, where she'd unwittingly discovered reverb), Barwick's gradually refined a process that is at once inventive and incredibly simple. She sings short, reverb-drenched, often wordless vocal fragments into a loop station (though she made the loops on the painstakingly lo-fi Sanguine using just a guitar pedal) and layers them into luminous compositions that feel like the aural equivalent of an airplane ride through a cloud. Toweringly sublime yet invitingly human, her music has an uncanny power to transform whatever space it's played in. It can make a cramped apartment feel like a high-ceilinged cathedral, or-- when she plays in one-- an actual cathedral feel like a gear-cluttered basement show.

Following the warm reception of The Magic Place, Barwick's approach has often been compared to ambient pioneers like Steve Reich and Brian Eno or the conceptual vocal artist Meredith Monk, but something about her music remains approachable and deeply personal—more intuitive than academic. Even as Barwick's songs become as polished and ambitious as those on her third full-length album, Nepenthe, they’ve managed to retain a certain playfulness and an openness to the process of discovery. It deserves mention among the best and most artful ambient music being made today, but Barwick’s work still feels like the realization of a dream left over from childhood, made by someone downright giddy that she has finally figured out a way to sing a round song with herself.

Sanguine, the 2009 EP Florine and The Magic Place all conveyed a sense of serenity found in solitude, which is maybe why her collaborations with other artists have been such a mixed bag. Her records with Ikue Mori (for RVNG’s FRKWYS series) and Helado Negro (as the duo OMBRE) have been solid, but a 2011 remix EP (featuring versions of Magic Place songs reworked by the likes of Diplo, Lunice and Prince Rama) basically just underscored how beside the point it is to remix a Julianna Barwick song. Her music is so pure and reliant on moments of quiet that another artists’ presence often overwhelms. So Nepenthe was a potentially risky move: It marks the first time she’s worked with other artists on one of her solo albums. And we’re not exactly talking anonymous session guys here: she recorded it with Sigur Rós collaborator Alex Somers (members of múm and the string quartet Amiina also contribute) at Sundlaugin, the band’s famed Icelandic “swimming pool studio.” (As a kid Barwick probably couldn’t have even imagined what sort of natural reverb you can get out of an abandoned swimming pool.)

Thankfully, Nepenthe sounds like a step forward for Barwick, a noticeable expansion in scope that still honors the sensibility that made her early records so unique. Somers’ lush production gives her music a larger and crisper depth of field, making it that much easier to get lost in its many overlapping folds. The structures of some of her tracks have become more complex: The billowing “The Harbinger” finds drama in the movement from crescendos to moments of quiet and back again, while the misty incantation “One Half” feels (true to its title) like a seamless fusion of two separate arcs. (For once, there’s even discernable lyrics in that song, but their purpose is purely phonetic, like words spoken in a strange dream.) But even in its most epic moments, one of Nepenthe’s greatest virtues is restraint. Given free reign in one of the most spectacular studios imaginable, Barwick didn’t go all kid-in-a-candy-store on us here. Nepenthe is a modest evolution-- the work of an artist growing, smartly, to scale rather than adding on needless bells and whistles or pushing prematurely past her limits.

It’s also more emotionally complex than her past work. The Magic Place was a slice of pure, unfiltered bliss, but the songs on Nepenthe ache and yearn. Album opener “Offing” hovers like thick fog over a remote pond, while Amiina’s strings drone and growl ominously throughout “Pyrrhic”-- these songs are still ethereal, but they’re stormier clouds than Barwick’s conjured before. On a few tracks, Róbert Sturla Reynisson from múm plays a guitar that, true to his post-rock pedigree, sounds more like a tiny spaceship or the noises made by a comfortingly unthreatening alien. But it’s Amiina’s presence that’s particularly harmonious with Barwick’s overall aesthetic. They're creative with the sounds they get out of stringed instruments, which allows Barwick to use them in a way that says something more complex than “[insert orchestral grandeur here].” They often feel like an extension of her own voice. “Waving to You”, the muted, palliative finale, fits in so well with Barwick’s vibe that it took me a few listens to realize it’s the only song on the album without vocals.

Barwick claims she went to Iceland with nothing written ahead of time. This is how she’s always worked, from her childhood experiments up to The Magic Place-- tapping into the vibrations of the present, and turning them into something that is somehow both enduring and impermanent. You sense feelings of longing and unease all over Nepenthe, which makes it a less blissful place to spend time than her previous album. But that also makes it a much more cathartic listen, and perhaps a more rewarding one.