A small series of recordings made in the late 1930s in Berlin proved to be of major significance. They carried the name of German conductor Wilhelm Furtwaengler to all parts of the world; they established that the Berlin Philharmonic was one of the world's best orchestras, and they guaranteed that if a complete recording of "Tristan und Isolde" were to be made, then Furtwaengler should be invited to conduct it. The complete recording materialized in 1952, but Furtwaengler never attempted a studio re-make of his 1938 recording of Tchaikovsky's Sixth Symphony.
Furtwaengler has an overall vision of the symphony's bleakness and sense of despair. Every subtle tempo fluctuation (and there are many, especially in the first movement) is addressed to helping achieve this vision. Virtuosity and brilliance are not displayed for their own sake, although Furtwaengler manages to ensure that a trumpet semi-quaver cuts through the heavy orchestral texture at Bar 246 in the first movement more accurately and tellingly than I have ever heard in other performances.
Mark Obert-Thorn's restoration work is exemplary. Some of the playing, especially in the Wagner performance, is very soft indeed, but even the tiniest signal emerges clearly here, well forward, and free of surface hiss.