When director Mike Mills began considering the music that would underscore his coming-of-age teen dramedy "Thumbsucker," he remembered a similar, albeit darker film: Hal Ashby's 1971 classic comedy, "Harold and Maude," which was scored entirely by singer/songwriter Cat Stevens.

Known primarily for his imaginative music videos for '90s hipsters (Air, Cibo Matto, Jon Spencer Blues Explosion), his graphic design and album art (Beastie Boys, Sonic Youth) and his affiliation with Spike Jonze's skate video crew, Mills was originally pegged as an ironist, but hopes the raw and emotional nature of "Thumbsucker" will clear the misconception.

Influenced by Ashby's movie, Mills sought a contemporary analogue to Stevens' folk-inflected songs, and settled upon indie-rock auteur Elliott Smith, who died of an apparent suicide in 2003 (see [article id="1479869"]"Singer/Songwriter Elliott Smith Dead; Friends, Fellow Musicians Pay Tribute"[/article]). Before Smith's death, the director approached the singer about scoring his debut film, and to his surprise, the reclusive Smith agreed.

"Elliott has always been an artistic hero of mine," Mills said from his home in Los Angeles, noting that he'd met Smith in 2000, when he designed the artwork for the singer's "Happiness" single. "I gave him the script and I was shocked that he liked it and wanted to work on it."

Then Smith, who had well-documented bouts with substance abuse, dropped from sight at around the same time Mills cast the film and began shooting in Portland, Oregon (ironically, Smith's former hometown). Coincidentally, by the time Mills had completed shooting the film, Smith began his recovery.

"I gave the script to him, and then he dropped off the face of the earth," Mills said. "He went through his whole crazy time, but by the time I was done with the film, he was making From a Basement on a Hill [which was released posthumously last year] and I was shocked that he was actually making music."

The two reconnected and Mills screened a working version of the film for an enthusiastic Smith. The plan to score the film was revived, only this time the pair came up with the idea of recording a series of covers. "We didn't even know if we could possibly afford getting all the rights to the music," Mills said, noting that Smith had planned to cover Leonard Cohen's "Sisters of Mercy" and an unspecified Neil Young song. "But that was the goal. It was just a crazy idea, but Elliott was so into it."

Smith was no stranger to soundtrack work: He garnered an Oscar nomination for his work on Gus Van Sant's 1997 film "Good Will Hunting" and was approached by Wes Anderson to record Beatles covers for "The Royal Tenenbaums," though the collaboration never came to fruition (the film did use Smith's composition "Needle in the Hay"). The singer gave Mills a version of Big Star's ballad "Thirteen" (previously released only as a snippet in the Jem Cohen short film "Lucky Three") and "Let's Get Lost," a track that would eventually surface on Basement.

In the last few weeks of Smith's life, he completed a cover of Cat Stevens' "Trouble" for the soundtrack, which is believed to be one of the last songs he ever recorded. According to Mills, Smith also began work on a version of John Lennon's "Isolation" before he passed away.

Distraught over Smith's death and left in the lurch for his soundtrack, the filmmaker attended a show by the Polyphonic Spree -- a group that includes a 20-odd-member chorus and performs wearing choral robes -- that left him electrified and inspired.

"[The show] really changed all the molecules in my body!" he enthused. "Their performance just made me feel like, 'Why not be happy? Why aren't you choosing to be positive?' I walked out of the theater and [felt], 'That's what I want people to feel like in the film.' "

Galvanized, Mills approached Spree leader Tim Delaughter about picking up where Smith had left off. Soon, the pair were creating a new vision for the film that would combine Smith's vocal songs with the Spree's choral-driven orchestrations.

"They rescued me, big time," Mills said of the Spree. "In more ways than one -- personally and the film's emotion. They provided the glue for the film."

To Mills, the balance of Smith's emotionally vulnerable covers and the Polyphonic Spree's inspiring score was the perfect balance for the film's tone. "The Spree is a lot darker than people [think], and Elliott was a lot more positive than most people associate him with being, and in a way they're both very Beatles-influenced, so it's all in a musical family."

"Thumbsucker" is due in theaters September 16; the soundtrack will arrive three days earlier and includes alternate and unreleased Polyphonic Spree tracks not featured in the film.

Track list for the Thumbsucker soundtrack, according to Hollywood Records: