“I hate musicals,” says singer and actress Marianne Faithfull in her low, whiskeyish voice. “Really despise them, detest them. I used to quite like them. . . . But recently it’s got so, so–” She gives a small but intense shrug of disgust. “Uhh! Andrew Lloyd Webber. Uchhh!”

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More usually teamed with an electrified pop band, the 43-year-old Faithfull is in Chicago this week for a concert with the classical chamber ensemble the Chicago Sinfonietta. The highlight of the program is The Seven Deadly Sins, a dramatic cantata that Weill and Brecht wrote in 1933. Though her mother (a descendant of the Viennese writer Leopold von Sacher-Masoch) was a dancer in Berlin at the time Brecht and Weill were active there, Faithfull says, she only became familiar with that material in the past few years: “If anyone had ever told me that I would be starting to do these kinds of things, I would have been amazed.” But Faithfull has never been one for making safe choices. She laid bare her own battles with drugs when she cowrote the grisly lyrics for the Rolling Stones’ “Sister Morphine”; and her career, launched when she was 17 with the recording of “As Tears Go By” (written for her by Mick Jagger, Keith Richards, and Andrew Loog Oldham), has ranged from challenging legitimate theater (Ophelia to Nicol Williamson’s Hamlet, The Three Sisters with Glenda Jackson) to innovative musical projects, including a track on Lost in the Stars, the anthology of Weill songs performed by pop musicians.

Faithfull has been compared to Lenya on numerous occasions; indeed, a review of Lenya’s 1933 performance of The Seven Deadly Sins in London could easily apply to Faithfull: “She has a strange voice with harsh notes in it, not a beautiful voice, but one with some curiously moving quality that cannot be analyzed.”

But these plans extend a few years into the future. “I always take my time with new projects,” says Faithfull, whose cultish following has developed from only a handful of records. “That’s how I am. I have to go slowly.” She has other irons in the fire as well–including collaborating with Osborn on an opera based on the legend of Persephone–and she doesn’t want to spread herself thin. “I feel very much with The Seven Deadly Sins,” she says, “that I have to be very, very focused and not think about anything else.”