This British-made archeological dig through the Stax archives is a major addition to the Booker T. & the MG's discography, a compilation of 25 cover tunes recorded on the wing and never released anywhere. In the course of backing the Stax roster's recording sessions, this tightly interlocked musical machine worked so efficiently that there was frequently plenty of studio time left over -- and not wanting to put it to waste, the quartet would come up with head arrangements of anything that happened to be on their minds. They're not fooling around or jamming aimlessly, either; these are all polished, concise, thought-out, radio-play-length performances that are at the very least up to the level of the filler on their mid-'60s albums. All but one of the titles ("Fannie Mae") are new to the MG's canon, and many will be surprising, like Petula Clark's hit "Downtown," retrofitted for a driving Memphis soul stew treatment, or the transformation almost beyond recognition of "You Are My Sunshine." The down-home soul workout of the Beatles' "Day Tripper" is especially effective, digging into the tune's blues roots, and Willie Dixon's "Spoonful" gets a deep-pile backwoods tread. Most revealing are the MGs' re-interpretations of two Sam and Dave hits on which they played: "Soul Man" sounds starkly stripped-down, shifting the balance of power over to Booker. T's organ, and "When Something Is Wrong With My Baby" spotlights Steve Cropper's dignified guitar. It's doubtful, though, that there were any lost-long potential hit singles in this batch; nothing leaps out at you with the originality of, say, "Green Onions," "Soul Limbo," or the inspired cover of "Groovin'."