So Gustav Mahler might have said about the Busoni Piano Concerto. I don't know if he ever conducted it but I wouldn't be surprised. There was mutual admiration. And as is rightly expressed in the sleeve-notes for this 1999 recording from Hyperion, this is more of a symphony with piano obbligato.
Writing the above puts me in mind of Berlioz's Harold In Italy (viola obbligato). Unlike Paganini, I can't imagine Liszt would have rejected the Busoni as unworthy, had he commissioned it. Liszt is a pertinent reference, beyond his legend as the greatest of piano wizards, because there is something faustian about this work, with its vast slow movement followed by an intoxicating scherzo - shades of Gretchen-Mephistopheles, in my imagination.
Hyperion index the slow movement, which lasts more than twenty minutes, across four tracks, making eight in total. The Brahmsian qualities of the concerto are well rehearsed, but I was picking up allusions to still more contemporary works: symphonies, Sibelius' 2nd and Bruckner's 9th. But this is a piano concerto that seems to have everything in it, and for all of its gargantuan length I was never bored. Calling it 'mahlerian' would surely be wrong, unnecessary: Busoni is in some respects a kindred spirit, however, and this is definitely an inspiration from Mahler's world. It deserves to be much better known.
Fortunately, there are several recordings in existence, starting with the pioneering Ogdon (EMI). My research before buying indicated that Ohlsson (Telarc) is equally highly regarded, and had it been available I might have been tempted by the live thrills of the Donohoe/Elder broadcast (EMI), but it was watching Hamelin play this on YouTube which decided me. The recorded sound is excellent, especially when I cranked up the volume. If you get a chance to sample, make it the fourth movement, the Italia scherzo, especially if you ever heard Joie du sang des etoiles (Messiaen) and got blown away.
Very special.