Among the many fascinating curios in this set heard for the first time, my new favorite is "Um Mitternacht" performed as if it were a sacred hymn by Aalte Noordeweier-Reddingus (she's a high mezzo, I'd say) and Anthon van der Horst on what sounds like the Mighty Wurlitzer (1928, Central Hall, Westminster, London) made for Columbia UK.
There's also a better remastering of the first ever recording of Mahler 4 than Denon's. Viscount Hidemaro Konoye's band (Tokyo New Symphony Orchestra) is small in number, and play. every. note. separately. with. almost. no. portamento. or. rubato. Mahler never sounded more like the soundtrack for some 1930s Ozu film that was never made.
Ward Marston's remarkable restoration of Ormandy's 1935 Mahler 2 makes the crazy-loud bells at the climax sound clear and yes, even crazy-louder. They really do drown everything else out. Other than that quirk, on its own terms, it's a remarkably "contemporary"-sounding performance (unlike the Viscount's 4th), but by today's standards, quick at 78 minutes.
I won't play everything in this set very often, but it is a treasurable thing for any Mahlerian to have. And it really is essential for Obert-Thorn's sterling work on all the Bruno Walter performances. Last thing to audition: Marston's stab at the Fried 2nd.