Wendy Lewis was as surprised as anyone when the Bad Plus asked her to sing on its new album -- especially since her previous experience as a vocalist came from fronting local rock bands, not jazz acts.

"My reaction went something like, 'Wow! Really? Hmmm...' " Lewis said, recounting a phone call last year from Plus drummer Dave King.

The end result of that call: Lewis sings on two-thirds of the jazz trio's latest CD, "For All I Care," which the group will promote with her Saturday at the Lakeville Area Arts Center and the following Saturday at the Cedar Cultural Center.

Not only was it a surprise the Plus men wanted Lewis, of all singers, it was more of a shocker that they wanted a vocalist at all. Heretofore, the New York/Twin Cities trio has performed and recorded and really done quite well for itself as an entirely instrumental act.

Less of a surprise: "For All I Care" is also entirely a covers album, featuring songs from the Bee Gees, Pink Floyd, Flaming Lips, Wilco, Yes and Nirvana. Reinventing well-known rock and pop songs has been a Bad Plus trademark since it raised Nirvana's "Smells Like Teen Spirit" on its 2002 Columbia Records debut.

Talking to King a few days after Lewis, the pieces all fit together better.

"After five studio albums that pretty well established our sound, we figured it was finally time to do some kind of collaboration," he explained. "But we didn't want to get the usual kind of jazz singer who would turn us into a backing band. We wanted a singer who would sound more like an extra instrument in the band."

The main inspiration for the record, King said, was the seminal 1963 album "John Coltrane and Johnny Hartman." As he described it, "The band still played like it was the John Coltrane Quartet, with or without Hartman. That's what we really aimed for."

With her more atonal and rhythmic style of singing, Lewis has a long history with King that made the unlikely collaboration easier to hash out. He drummed behind her in the '90s art-rock band Rhea Valentine. She also once performed with King's other jazz trio, Happy Apple, which features her nephew, Mike Lewis -- who also performed with Wendy in her more recent band Redstart. (Got all that?)

"There was a lot of trust involved -- trust from them in me, and trust that if it didn't work out, nobody would walk away with hurt feelings," Lewis said.

Lewis knows she will eventually have to take a hike, though. The Plus already plans a collection of all-original instrumental compositions as its next album. A second volume of tracks with Lewis could emerge down the line. Whether or not that happens, though, Lewis said, "I'm happy just to have taken the risk this one time and see it pay off."

Chris Riemenschneider • 612-673-4658