Like Paul McCartney’s 2002 tour, Simon & Garfunkel’s recent reunion shows delivered both nostalgia and immediacy. And like McCartney’s Back in the U.S., S&G’s Old Friends seems to flatten the vivid performances into aural Polaroids. The 25-track double album is undercut by its soft-focus sound, haloed by distancing room echo, which diffuses the musical drama rather than capturing it. The mix works reasonably well on intimate acoustic numbers like “Old Friends,” “Kathy’s Song” and “Scarborough Fair,” which trade in gossamer, but it has a deadening effect on “A Hazy Shade of Winter” and “Mrs. Robinson,” which require punch, and “America,” which calls for breadth. Too often, the masterful stage band, anchored by drummer Jim Keltner and bassist Pino Palladino, seems to be playing in the next room. Nonetheless, during quieter moments, the duo’s undiminished voices and Simon’s still-sublime playing are spellbinding as ever. Simon’s songs haven’t lost anything, either.