Schnabel plays the Adagio in a way that is consistent with the revolutionary and forward-looking nature of the entire piece and with his reading of the outer movements. It’s well known that Schnabel insisted on playing the first movement according to Beethoven’s metronome marking; in his headlong assault not only does he avoid the ponderousness that drains the movement of energy at a slower tempo, he captures the qualities of urgency and abandon that Beethoven put into this movement.
In the Adagio Schnabel is particularly sensitive to registration; when the outer voices are widely separated he adjusts the balance so that both are always clearly heard. Extreme separation is a characteristic of this movement and a new way of deploying sound; the sheer spaciousness gives the movement an abstract quality and is one of Beethoven’s revolutionary additions to the sonic landscape.
When it comes to the fugue of the Hammerklavier (which starts at 32:09 in the YouTube performance) it is a commonplace to criticize Schnabel’s playing with mock or real horror. But I believe that his playing is defensible in the context of his approach to the entire piece. Schnabel apprehended Beethoven’s Expressionistic rendering of a fugue and played it as such. The bold smearing of contrapuntal motives is completely in keeping with Beethoven’s dissonant and free adaptation of the fugal form in this movement, which he marks modestly as “Fuga a tre voci, con alcune licenze”, “with some license”.
I don’t want to make too much a point of this but the fact that Schnabel was active during the time of the major movements in early 20th century art, Expressionism, Cubism, Futurism, must have prepared him to hear and play the extremes that Beethoven put into Op. 106.
Against this backdrop, but in view of the fact that Schnabel really does drop a lot of notes and in deference to the measured pace of Duchamp’s “Nude Descending a Staircase, No. 2.”, perhaps it’s more fitting to think of Schnabel’s version of the last movement of the Hammerklavier as “Fugue falling down stairs”.