Since the split of Led Zeppelin, Robert Plant has deftly sidestepped pigeonholing as a mere purveyor of classic rock, preferring instead to indulge his mercurial interests in everything from old-school psychedelia to swing to Eastern ragas. This two-disc retrospective of Plant's solo career touches on all those aspects, painting a picture of the artist as an exceedingly adventuresome -- if no longer so young -- man. In recent years, he's been prone to more mystical musings, and as evidenced by his versions of Tim Buckley's eerie "Song to the Siren" and Jesse Colin Young's oft-covered "Darkness Darkness." Both evince a different side of Plant's trademark higher register, a facet that's icy and desolate, rather than horn-doggedly wailing. Plant doesn't ignore his libidinous nature altogether, of course, delivering songs like "Tall Cool One," "Big Log," and the previously unreleased "Upside Down" (which dates from the same mid-'80s period). The singer showcases his facility with rock chestnuts on soundtrack offerings such as "Louie, Louie" (recorded for Wayne's World 2) and "Let's Have a Party" (culled from The Last Temptation of Elvis). The set's real revelations, however, come in its surfeit of archival material, including versions of "Hey Joe" and "For What It's Worth" (both of which feature a pre-Zep John Bonham on drums) and Plant's first single, 1966's "You Better Run." And just to prove he hasn't lost the spark that's burned within over the decades, Plant includes a freshly recorded live rendition of "Win My Train Fare Home," recorded during his stopover in Timbuktu. Whether the air is as smoke-filled as in a Route 66 juke joint or as rarefied as in the Himalayas, Plant provides the right soundtrack to cut through.