How is one supposed to play this exactly?
One can neither can play a 14th in the right hand (my hands are not that big) nor play legato parallel 10ths in the left; hence some sort of arpeggiation is required. But I can’t quite seem to reproduce how Glenn Gould plays this measure. Then again, that phenomenon is not unique to this passage.
Play the notes between the hands as they are in the staves, except play the F at the beginning of the second measure with the left hand.
Surely F4 to D6 is a 13th (XIII)?
By Golly, you’re right. I’m going to have to use that example next time I teach algebra, namely, that the group law of intervals is isomorphic to $latex \mathbf{Z}$ but the group law is given by
$latex (x \star y) = x + y – 1.$
(I guess it’s even worse than this, because three thirds is not and eighth…)