In the fall of 1969, Simon and Garfunkel launched their last tour for more than a dozen years — the duo would break up months later, shortly after the January 1970 debut of their biggest-selling album, Bridge Over Troubled Water. Six of those final tour stops were recorded for a planned live follow-upto Bridge, but this is the first time that album has been released. Like now, the nation was polarized then: The Vietnam War was raging, campuseswere ablaze and generational lines were drawn. Also like now, anyone seeking to build a bridge, as Simon and Garfunkel did, was accused ofbeing soft. But songs of such generosity were essential: The delicacy of Art Garfunkel’s voice on “For Emily, Whenever I May Find Her” and “Scarborough Fair/Canticle” is an apt metaphor for the fragile bondholding this partnership — and the country — together. Meanwhile, the street-wise cadences of “The Boxer” suggest the coming ofdarker days. The audiences gathered for these sets were hearing “Bridge Over Troubled Water” for the first time, and their amazement at itsbeauty is palpable. Nearly forty years later, the song sounds appropriately elegiac, even somewhat restive — a requiem for what might have been and solace for what was yet to come.