The boldest sentiments are only worn on the sleeves of bold people. Greta Kline may not perceive herself as bold, but her gentle-crooning music outfit Frankie Cosmos sure is. The 19-year-old has been churning out album after album of material for almost five years and what’s now collected over that time on her bandcamp page has something of a journal-esque quality to it. But the journal isn’t necessarily hers.

“Frankie Cosmos is like a braver, cooler version of me,” Kline says.

While all of the music released under the name Frankie Cosmos is essentially just bedroom recordings of Kline, she finds that assuming this alter-ego benefits her own songwriting.

“If I didn’t have this alter-ego, I don’t think I’d be able to emotionally put things out there as much,” she says. “I can kind of hide behind things by saying, ‘it’s not me, it’s Frankie Cosmos.’”

Make no mistake, there is no reason for a songwriter like Kline to feel uneasy about her creativity. The library of recordings that makes up her bandcamp yields song after song of earnest, but coy lyricism, approaching each tune with big eyes and a tender heart. The fragility of the recordings is only heightened by her feathery vocals that thread the needle between Kimya Dawson and the softer tones of Dolores O’Riordon. The themes she tackles, which range from restless suburban angst to the comparisons of Justin Bieber fandom and religion, show Kline’s imaginative brawn and her confidence in the feeling of being unconfident.

The prolific bandcamp catalog of Frankie Cosmos has spread amongst an Internet community far beyond her Manhattan bedroom, where most of the recordings were born with the simple push of a button on GarageBand. Kline has also been in the New York-based Porches, a band led by her boyfriend Aaron Maine, for about a year and a half. From a year packed with constant touring and recording with both acts, Kline has created significant waves, to the point where she will now be releasing her first official album, “Zentropy,” in March on Double Double Whammy Records. The material on the album will be a mixture of entirely new tracks and songs pulled from previous self-releases. “It’s nice to have years worth of demos to kind of pick out the best stuff to re-record,” she says. “I can look at it as kind of a warm-up.”

Kline has already premiered a single called “Owen” on Pitchfork, but as she awaits the full release of “Zentropy,” she continues to gig heavily throughout the northeast. She will play Great Scott tomorrow night with a full band that includes Maine on guitar. She joins an impressive bill of headliner Mutual Benefit, which released one of 2013’s best with “Love’s Crushing Diamond,” and Krill, who Kline covered on May 2013’s “told you so.” It’s your first chance to hear Greta Kline — and meet Frankie Cosmos.

Frankie Cosmos – Buses from Rookie on Vimeo.