We have to take on faith while watching this telecast that the legendary staging by Giorgio Strehler with sets by Luciano Damiani that opened the 1975 Scala season really was all that. Live television wasn’t sophisticated enough a half-century ago to capture the chiaroscuro dimmed lighting nuances and intricate spatial relationships that made Strehler’s contribution so revered. But the purely musical performance preserved here is thrilling, ratcheted to a higher intensity than the Deutsche Grammophon studio recording. Verrett is white hot; Cappuccilli and Ghiaurov are more involved, and Luchetti is strong as Macduff. But Abbado shows how a conductor can masterfully shape a Verdian musical-dramatic arc while allowing it to breathe moment to moment. The fact that his motor consistently runs a bit faster here in ensemble scenes than on the DG recording gives us the (entirely appropriate) sense that he is plunging everyone toward a great, gaping abyss. And the Scala chorus, orchestra and audience are clearly all buying and totally committed to whatever pozione di streghe he’s selling them (and us).