Seven albums and 17 years into her recording career, Dar Williams certainly has a body of work that justifies a "greatest-hits" album, but she's opted to do something a bit more ambitious than just slap a bunch of her best-known tunes onto a CD. Many Great Companions is a two-disc set, with one disc collecting 20 songs from Williams' previous albums that have become fan favorites over the years, and the other consisting of new recordings of 12 tunes from her catalog (six of which appear on both discs), performed in stripped-down acoustic format with a few guests, including Mary Chapin Carpenter, Patty Larkin, and Gary Louris of the Jayhawks (who also co-produced the new material). Though the new recordings are well done, the nature of the performances puts the focus on Williams' folky side, at the expense of the pop- and rock-influenced material that has represented some of her best work; Williams has been fortunate enough to work with producers who've fleshed out her songs without burying their lyrical and melodic strengths, and the no-frills versions of "Spring Street" and "What Do You Hear in These Songs" sound like pale shadows of the originals. Also, some of the numbers, such as "The Babysitter's Here" and "When I Was A Boy," were not especially far from solo acoustic recordings in the first place, and while Williams is a more confident and nuanced vocalist in 2010 than she was in 1993 when those songs were recorded for The Honesty Room, the differences are not so dramatic to keep the new recordings from seeming like footnotes in comparison to the original versions. However, both discs offer abundant evidence that Williams has been one of the best singer/songwriters to come out of the contemporary folk scene in the past two decades, and her material -- heartfelt, soul-searching, and often witty and full of fascinating detail -- is invariably impressive stuff. Ideally, Many Great Companions would be best purchased by two people going halves on the set -- a devoted fan who wants to hear the new recordings can take disc one, someone unfamiliar with Williams can take disc two, and they'll both go home with something likely to please them.