PARK CITY, UTAH -- Jenny Lewis' old band Rilo Kiley provided the springboard sound for Naomi Foner's film "Very Good Girls," but it's all-new material that drives the rest of the flick.

Premiering at Sundance, "Very Good Girls" stars Dakota Fanning and Elizabeth Olson, and with the girls' coming-of-age tale along with the female director's debut, Lewis set out to have a "strong female voice" to her songs -- even if she didn't spend much time singing on the largely instrumental tracks. Lewis wrangled in some backup singers and took cues from legendary soundtracks like "Harold & Maude" and some newer composers to dive in.

"I think of 'There Will Be Blood' and Trent Reznor's works when I think of these song-based scores," she told me in Park City. "Using old ideas, they speak to a certain generation."

As for new solo material -- since Rilo Kiley has broken up -- Lewis says she's halfway through recording a new album, and is "forming the concept as we speak right now. I love collaborating, so there's a whole cast of characters that I've toured with, played with in the past. It's a village effort."

Lewis' last solo album, "Acid Tongue," dropped via Warner Bros. in 2008, boasting of contributors like Zooey Deschanel and M. Ward (of She & Him), Chris Robinson, boyfriend and songwriter Johnathan Rice and Elvis Costello. She also released a duo album Jenny And Johnny with Rice in 2010, "I'm Having Fun Now."

Lewis also strongly hinted that she's joining "old friends" the Postal Service for tour in 2013. She said that it had been "10 years since we've played a show," and that she'll be needing to dust off her synthesizer for the stint. As previously reported, synth-pop crew the Postal Service (DNTEL and Death Cab For Cutie's Ben Gibbard) have reconvened for the Coachella Valley Music and Arts Festival in April, and are planning on skedding further tour dates for those who can't make the double-weekend event. Jenny Lewis sang on their sole album "Give Up."

"I'm very excited," she said of the mysterious reunion.