FOR three decades Joni Mitchell wrote songs that were equally daring in their personal revelations and their musical restlessness. They traced a woman's romantic and intellectual life in progress, from bright-eyed aspiration to cosmopolitan wanderlust to political bitterness, from folky sweetness to pop sheen to open-ended, jazzy excursions. Along the way her music spawned countless disciples and admirers, among them Herbie Hancock, who is releasing a tribute album, "River: The Joni Letters."

But after her 1998 album, "Taming the Tiger," Ms. Mitchell fell silent as a songwriter. She was suffering from the muscle degeneration of post-polio syndrome, having had the disease as a child. She called the music business and its star-making machinery a "cesspool," and she completed her major-label contract with albums of cover versions and remakes. Her last one was "Travelogue" in 2002.

The album "Shine," due out on Sept. 25, will break the silence. (It's the first release in a two-album deal with Starbucks Entertainment's Hear Music label.) Describing its opening song, "One Week Last Summer," Ms. Mitchell wrote on her Web site that she was in a house by the sea, looking at seals and flowers, when a bear arrived to rummage through her garbage. "That night the piano beckoned for the first time in 10 years," she said.

The new songs are not happy ones; they worry over war, the environment and a bleak future. "What's coming out of me is all sociological and theological complaint," she told an interviewer. But the music isn't strident; it's inward-looking and rhythmically complex.

Some of her new songs are part of "The Fiddle and the Drum," a collaboration with the Alberta Ballet that is named after her antiwar song from 1970. The ballet also incorporates Ms. Mitchell's paintings, which will be exhibited in New York this fall. As she makes her voice heard again  lower, darker and far more knowing  she continues her evolution from Candide, hoping for the best, to Cassandra, foreseeing disaster.