Sarah Jarosz was 18 and doe-eyed when she released her debut album, just a few months before she also entered her first year at New England Conservatory. At the time, the rising singer-songwriter and mandolin player, who also holds her own on guitar and clawhammer banjo, seemed a little on the fence about the decision. “I definitely did ponder the idea of just going straight into the music career,” she told the Globe in 2009, shortly after arriving here from her native Wimberley, Texas, not far from Austin. “But there’s always more to learn, and I also didn’t want to miss out on the college experience.” Four years later, Jarosz has recently graduated – not only from college but from Americana’s minor leagues. “Build Me Up From Bones,” her forthcoming third album for Sugar Hill Records, is the work of an artist who has developed considerably as a writer, singer, and multi-instrumentalist. She’ll celebrate its release with a show at the Sinclair in Cambridge on Sept. 14. Jarosz, 22, credits her palpable growth to the range of her studies at NEC. Already steeped in folk and bluegrass and rock, Jarosz stretched beyond her comfort zone, into the realm of classical music (Stravinsky and Schoenberg, Debussy and Ravel), and she dug deep into art and poetry. “It’s nice to have the outlet to be creative in a nonmusical setting,” Jarosz says recently, adding that she had gotten especially close to her poetry/art teacher. “We would have conversations about the similarities and differences between writing poetry and lyrics. For me, it was an extremely different process writing poetry. I didn’t have a ton of background in poetry, so I felt like I was coming at it from this place of freedom and not being tied down to a technique or formula. It definitely influenced my writing.” Jarosz says this a few weeks ago in the picturesque courtyard of the Museum of Fine Arts, where she has chosen to conduct the interview and have her portrait taken. The next morning she’ll drive off in a U-Haul for her next adventure: moving to New York’s Upper West Side to take her post-collegiate career even farther. She has the glow of someone who’s enjoying summer’s waning days — and her new life as a graduate. She earned a bachelor of music degree in contemporary improvisation, the same program that Crooked Still’s Aoife O’Donovan, who was an early supporter and mentor, had pursued. With due respect, “Build Me Up From Bones,” which will be released on Sept. 24, makes Jarosz’s first two albums sound like she was merely tuning up. There were surprises along the way, from veteran session player Dan Dugmore contributing seductive steel guitar to co-writing songs with established musicians such as Darrell Scott and Jedd Hughes. O’Donovan sings lovely backing vocals throughout. And a pair of covers – of Bob Dylan’s “Simple Twist of Fate” and Joanna Newsom’s “The Book of Right-On” – speaks to Jarosz’s influences both classic and contemporary. At the heart of the record, though, is the chemistry she shares with her bandmates, whose presence is far more pronounced this time around. “I think a big part of [my growth] has to do with how much the two guys who tour with me, [violinist] Alex Hargreaves and [cellist] Nathaniel Smith, play a lot bigger role on this record,” she says. “And that really does feel like coming into my own because that’s what I’ve been working on for the past three years. It really feels like my sound.” Gary Paczosa, who’s vice president of A&R for Sugar Hill Records, produced the new album, along with Jarosz’s first two efforts. He also signed her to the label when she was still a teenager. “Her development as a writer has grown, but more than anything it’s been her confidence in her vocals. She’s singing so much more. When I was working with her early on, she wasn’t really singing,” Paczosa says. “By the time we got to the third record, she had great control and confidence and could easily make changes if I threw out different ideas. She was much more adaptable this time because she has a fine-tuned instrument now.” On “Song Up in Her Head,” her debut, and its 2011 follow-up, “Follow Me Down,” the songs originated with Jarosz and then she and Paczosa built them up with overdubs and adornments. Her latest is more organic, a trio setting that emphasizes the value of space. The songs breathe. From the perspective of composition and structure, the music is more complex and nuanced, too. Jarosz’s voice, warm and elastic, rings out strong and clear. “I’m really curious to see what happens with this album,” she says. “I feel the most confident about this record in terms of my own vision of it and believing in it. I think it does open up from the last two. I really hope that people love it.” James Reed can be reached at [email protected]. Follow him on Twitter @GlobeJamesReed. .