What an ingenious idea. As a way of “benefiting American Veterans of the Vietnam War,” D.C. label Exotic Fever paired up each of 20 artists, many out of the local scene, with a song from the Vietnam era. The resulting compilation brings the spirit and energy of the ’60s into the 21st century and filters all the emotions and ideals of those times through latter-day sound, fitting (and all too relevant) in an age that experienced similar — though, at once, entirely uncharted — questions regarding war. Some of the new takes perhaps play it too safe, or have little chance of bettering original recordings by, for instance, Led Zeppelin, Buffalo Springfield, or the Beatles. (There are, on the other hand, fairly straight but stellar versions of Neil Young, Todd Rundgren, Creedence Clearwater, and Simon & Garfunkel songs.) As is usually the case with tribute collections, the covers that most radically reimagine their source material provide the most thrilling moments on Don’t Know When I’ll Be Back Again. In this case, top honors belong to the mind-blowing synth pop version of “1969″ by the Gooses, a riot of Moog runs, stilted drum machine beats, and Atari vocals that could not be any further from the Stooges original, though it is, in its inimitable way, just as drastically punk. Nearly as impressive is the densely ambient “White Rabbit” from Enon, a much different sort of head trip than the Jefferson Airplane version, a gloomily gothic “I Feel Like I’m Fixin’ to Die Rag” from the Panoply Academy Legionnaires that puts Country Joe through a calliope, the Rouge’s melancholy torch version of “Happy Together,” and Beauty Pill’s murky dub take on Jimi Hendrix’s “I Don’t Live Today.” Also of note are the artists who delved more deeply into the era’s songbook, pulling out less obvious selections by John Cale (“Fear Is a Man’s Best Friend,” beautifully rendered by J. Robbins), the Spinners (the Reputation transforms “Games People Play” into a beguiling lounge duet), folkie Malvina Reynolds (a Salvation Army-esque “Little Boxes” from the Dorian Wood Guilt Trip), and Jimmy Cliff (Ted Leo’s gorgeous, falsetto “Many Rivers to Cross”). – Stanton Swihart