Mary Lou Williams, whose arrangements for Andy Kirk were among the most prescient of the swing era, never led her own big band. In 1967, Duke Ellington lent her hisno mere act of gallantry, because he was probably eyeing her as a potential replacement for Billy Strayhorn, who'd died that year. Ellington never got around to recording any of the pieces he commissioned from Williams or adding any of them to his concert book, which is both a shame and a mystery, because the four premiered on the Dutch Jazz Orchestra's The Lady Who Swings the Band (including updates of two composed in the 1940s) capture both the depth of color and the air of intellectual inquiry we associate with Ellington circa The Far East Suite. Matter of fact, all of the unearthed Williams presented here could pass for Ellingtonia, as could the remakes of two of her charts for Kirk and one for Benny Goodman. Chalk this up to the DJO being Strayhorn specialists (three previous CDs' worth). But it also suggests Williams was as intrepid as Ellington right from the start, and as close to his equal as anyone. The most veering and far-reaching of the premieres is "Shafi" (1977), and check out the final band chorus on "Walkin' and Swingin'," first recorded by Kirk in 1938, if you want to know where Monk lifted that tricky pattern for "Rhythm-a-Ning."