Beethoven’s 16 string quartets constitute a body of music that remains one of the towering edifices of Western art. The so-called Middle Period works—the three “Rasumovsky” quartets and two stand-alones, Op. 74 (sometimes called “Harp”) and Op. 95 (“Serioso”)—sit between the early and still traditional Op. 18 group and the transcendental and searching late works. The “Rasumovsky” quartets, written for the Russian ambassador in Vienna, are witty and extraordinarily inventive with almost symphonic ambitions. Op. 74 is a slighter work of great charm. The Takács Quartet’s set is magnificent, a wonderful example of quartet-playing of truly sublime quality and achievement.