Tom Rush emerged from the ‘60s Cambridge folk scene and established himself as a master interpreter with his exemplary 1968 album The Circle Game, where he drew attention to the songwriting of Jackson Browne, Joni Mitchell, and James Taylor. Though he soldiered on through the ‘70s with equally enticing material, Rush was never a prolific writer or recording artist. What I Know is his first studio album in over 30 years and sounds as if it could have been birthed in the ‘70s alongside the rest of his catalog. The voice is in fine form — it remains the definition of “warm.” The arrangements are every bit as restrained and tasteful, unpretentious and serving the songs with great understatement. Emmylou Harris, Nanci Griffith, and Bonnie Bramlett guest harmony on a track apiece, but Rush remains the central star. His unhurried delivery mixed with the country-folk arrangements make for wistful tunes (“River Song,” “Too Many Memories”) that evoke images of a wise, old acoustic troubadour settled in the corner of the club. Positively exquisite.