Many music fans salivate at the mention of those who presaged the concept of roots-consciousness. Gram Parsons, one of Americana's forefathers, envisioned "cosmic American music" (his words), a holy blend of country, rhythm & blues, rock 'n' roll, and gospel. Why Taj Mahal is not more often mentioned as a "roots progenitor" is a mystery, as his approach has encompassed electric and acoustic blues, blues origins in African music, gospel, and assorted Caribbean, Hawaiian, and Afro-Latin styles, and he's been at it since 1968. To commemorate his 40th year in music, Mahal (born Henry St. Clair Fredericks) gives us Maestro, a career retrospective (though not a "best of" set). There's a slew of big-name guests leaning a hand — including Ziggy Marley, Ben Harper, and Los Lobos — yet make no mistake: It's the Taj man's show all the way. Lean-and-mean urban blues is represented by "Scratch My Back" and "TV Mama," Mahal's vocals rich with a ribald Howlin' Wolf-like rasp. "Zanzibar," a duet with African diva Angelique Kidjo, interlaces assorted West African styles seamlessly, sparkling kora dancing with electric guitar riffs and an Afro-rumba beat. The loping "Slow Drag" highlights the banjo's presence in the blues continuum, and "Hello Josephine" is his rollicking tip of the fedora to New Orleans. There's a lot to take in here, but it's fun and educational at the same time.