For the record, Diana Krall isn't wearing bordello lingerie on the cover of "Glad Rag Doll" (Verve), nor is the scanty attire a cheap trick to hawk her new album. "I was just playing dress-up to illustrate the album's title and 1920s theme," said the 47-year-old jazz-pop singer-pianist and mother of two. "There isn't even any cleavage—just a little more thigh. Look at Alfred Cheney Johnston's Ziegfeld Girls photos from the period. They're much more risqué."
On "Glad Rag Doll," due Oct. 2, the breathy-voiced two-time Grammy winner covers mostly jazz and vaudeville songs written between the two world wars. But the album's bluesy, Prohibition-era theme is a risky deviation for Ms. Krall, whose fans have grown accustomed to her humid renditions of American Songbook standards backed by lush orchestrations.
"I'll be back to strings—this album is just something I wanted to do in addition to that," she said. "I'm not trying to reinvent myself here. The more different creative outlets I have, the more exciting recording is for me. This is the music I was first attracted to—before Louis Armstrong and Nat Cole."
Born in 1964, Ms. Krall grew up in British Columbia and today divides her time between Vancouver and New York with husband, Elvis Costello, and their children. As a preteen, Ms. Krall spent hours listening to her father's vast collection of 78-rpm records. Fascinated by the '20s and '30s, she traveled at age 16 to Williams College in Massachusetts to visit the archives of jazz-age band leader Paul Whiteman.
"It had nothing to do with Whiteman, though—I was intrigued by Bill Challis's complex arrangements for the band," she said. "When I saw the scores and harmonies he wrote and the parts for [cornetist] Bix Beiderbecke, I got chills."
In preparation for her new album, Ms. Krall selected 35 songs from her father's collection and gave sheet music to producer T Bone Burnett. "I had no idea which songs T Bone would choose until I arrived at the studio," she said. "We wanted the element of surprise and improvisation."
"We Just Couldn't Say Goodbye" and "Just Like a Butterfly (That's Caught in the Rain)" were inspired by the relaxed recordings of '20s singer Annette Hanshaw. There are nods to Bing Crosby, Gene Austin and Cliff "Ukelele Ike" Edwards.
Breaking theme, Mr. Burnett suggested Betty James's 1961 rockabilly single "I'm a Little Mixed Up." "Playing rock 'n' roll piano on there was a challenge," Ms. Krall said. "It's not like jazz improvisation. It's all mood, guts and blood." Ms. Krall also took on Ray Charles's "Lonely Avenue" from 1956—with an arrangement that references Miles Davis's album "A Tribute to Jack Johnson." As for the title track, it was first recorded in 1928 by vaudeville clarinetist Ted Lewis—with lyrics she calls "a feminine statement, in a weird way."
What does Ms. Krall's father think of the album? "He likes it. Last week I was with him for four hours listening to stacks of old 78s. This album is who I am. It just took 40 years to make."
A version of this article appeared September 21, 2012, on page D5 in the U.S. edition of The Wall Street Journal, with the headline: Diana Krall Sings With No Strings Attached.