Pouring herself a cup of herbal tea at a downtown restaurant, Sara Bareilles is the picture of serene composure. You’d never guess that she’s been working like a maniac for the better part of two years.

The singer/songwriter of empowering hits such as “Brave” and “Love Song” began unveiling the fruits of that labor in 2015. The stage musical Waitress — an adaptation of the 2007 Adrienne Shelly film, with music and lyrics by Bareilles — opened at Cambridge’s American Repertory Theater in August 2015. In October, Simon & Schuster published Sounds Like Me: My Life (so far) in Song, a collection of “confessional” essays. Shortly thereafter came the release of What’s Inside: Songs From Waitress, featuring tunes from the musical — which opened on Broadway in Spring 2016.

“It was an act of self-indulgence,” Bareilles, 35, says of the album, which was released last month. “I couldn’t quite pass off the show without getting a chance to sing these songs myself.”

Bareilles was first approached about the book and musical during the same period — ironically, while taking a “mini-hiatus” from recording and touring. “I was hanging out with my sister,” she recalls, when she was contacted by her literary agent and by Diane Paulus, the Tony Award-winning director of recent Broadway revivals of Pippin and Hair, regarding Waitress.

Though a fan of musicals since childhood, with favorites ranging from Oklahoma! to Chess, Bareilles had never seen the film Waitress before. Watching it, she was immediately attracted to the heroine, Jenna (played by Keri Russell), an inventive pie maker trapped in an abusive marriage.

“I really loved how flawed and messy Jenna is,” says Bareilles. “I liked that she was a soulful, creative person trying to find an authentic way to express herself.” She also found “so much natural similarity between the character and myself that it wasn’t a stretch to find my way in” to eventually record the songs herself. “She’s someone who has a great capacity for love, but feels very broken sometimes.”

Bareilles had first seen the actress who would play Jenna on stage, Jessie Mueller, in Mueller’s Tony-winning performance in the title role of Beautiful: The Carole King Musical. “She was so grounded and graceful, and just had so much heart,” Bareilles says of Mueller, who has become a good friend.

Both Waitress‘s leading lady and its composer/lyricist earned good notices in Cambridge, though Bareilles hasn’t read them. “I don’t really read reviews. My theory is that the good ones inflate your ego, and the bad ones can just ruin you. I’ve found it’s more productive to stay in the room with what I’ve created, rather than worry about how it’s being perceived.”

That perspective did not come without a few hurdles. In Sounds Like Me, Bareilles recalls personal and professional challenges stemming back to her struggles with weight as a child. “I have two young nieces, and I can remember so vividly what I went through, with body image and peer pressure,” says the singer, whose figure is now slim and chiseled. “I really want to be someone who can send positive messages, who can encourage them to love themselves as best they can.”

Working on Waitress made Bareilles realize how much she herself has grown since her 20s. “I’m about to have my first Broadway musical. When I made my first album, I was so overwhelmed that I don’t think I was able to enjoy it. It’s nice to be in a place where I can create something new and realize how precious it is.”

Elysa Gardner is a staff reporter for USA Today, where this story first appeared. 

Buy tickets to Waitress at Broadway in San Diego.