There are now two instances in which I presume Beethoven to have intended a slur when, in fact, there is none. The first I was aware of was in his First Symphony, in the Minuet movement. The second I heard this morning, again in a Minuet, from Piano Sonata in D, Op. 10, No. 3. Two left-hand chords, the first long, the second short, in a set-up that had "SLUR" written all over it.
Except that in each case there was none.
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The first case was vivid enough to cause me to check to score when I returned home from the concert. It was, in fact, the most vivid single event of the whole evening which was singularly lacking in humor, except for this one detail. It is true that I went to the all-Beethoven concert out of curiosity to see whether a conductor of my generation (in fact, a classmate from Oberlin) could actually get the NYPhilharmonic to observe Beethoven's articulations correctly after lifetimes of doing them by ear, i.e., a la 19th-century esthetics, i.e., wrong. To my surprise they did very well, the proof being that this one absence-of-slur stood out.
The second instance involved my young computer animator student: After going to some pains to get him to finger the chords so as to connect them so as to assure the proper balance between them, he played the progression perfectly as notated, unslurred, and burst out laughing. "That is the point of the whole piece!" Deception. Surprise.
In each case unforgettable delight.
I wouldn't have missed it for the world. Neither would he. Took some digging but yielded pure gold.