‘CSN’: An Impressive Array

The foundation of “CSN”--the new four-disc retrospective on Atlantic of the musical alliance formed in the late ‘60s by David Crosby, Stephen Stills and Graham Nash--is an array of the rock trio’s best-known recordings.

The selections--some of which feature sidekick Neil Young--range from the wistful “Teach Your Children” and “Our House” to the more urgent and vigorous “Ohio” and “Long Time Gone.”

As with many of the most appealing box sets these days, however, that’s just the starting point. Other key elements: more than two dozen previously unreleased tracks, and the artists’ written comments on the songs.

Among the extras: original mixes of “Suite: Judy Blue Eyes” and “Woodstock,” an early demo of “Guinnevere,” live studio renditions of “Helplessly Hoping” and “Blackbird,” and three previously unreleased songs.

The comments in the accompanying booklet are often equally engaging.

About “Helplessly Hoping,” Stills notes: “This song was inspired a long time ago by my 10th-grade English teacher in Tampa, Fla. She was a real knockout, so much so that she got all the football players to stand up and read poetry, trying to impress her with how sensitive we were and how much we loved this awful stuff.”

Reflecting on Young’s “Ohio,” which was inspired by the fatal shooting of four students by National Guard troops at Kent State University, Crosby says, “I was with Neil at a friend’s house and handed him Life magazine with the Kent State photos. He was silent for a long time, then picked up his guitar and 20 minutes later had this song. . . . For me, ‘Ohio’ was a high point of the band, a major point of validity. There we were, reacting to reality, dealing with it on the highest level we could--relevant, immediate. It named names and pointed the finger.”

Rather than showcase only the material recorded as a trio or quartet, “CSN” contains various songs recorded by the individual members in group or solo settings. These tunes range from Stills’ “Love the One You’re With” and “Change Partners” to Nash’s “Military Madness” and Crosby & Nash’s “Immigration Man.”

The material on the album is quite uneven once the selections move beyond the early years together, but the group’s trademark harmonies--applied with equal grace to love songs and social commentaries--remain among rock’s most endearing and distinctive sounds.