The great classic master of Beethoven with the great modern master.
I am not generally a proponent of slow Beethoven. Much as I often love Furtwangler's recordings, I find many of his Beethoven performances overvalued to the point of absurdity - Furtwangler simply does not find the lightness or the humor in Beethoven, his performances are almost unrelentingly grim. But when masters like Klemperer and Barenboim present Beethoven with a complete understanding of all his facets, they can take whatever tempo they like. And in this case, here is a complete understanding of the facets of Beethoven's Emperor Concerto.
The greatest music can take all sorts of interpretations. Another of the very finest recordings of this work is Robert Levin's period instrument performance with John Eliot Gardiner conducting his Revolutionary and Romantic Orchestra. If Barenboim/Klemperer tends toward the solid, dramatic and massive, then Gardiner/Levin tends toward the intimate, spontaneous and limpid. But both retain within them qualities of the other. In their ways, both of them deserve the moniker 'great performances.'