Its an amazing soundscape of percussion and pianos, pushing what the instruments are capable of. All of the parts are given equal importance and they are hard to play. It sounds quite impenetrable and is absolutely frantic. But once you have heard it few times and know that Bartok was very keen on the Golden section, and the Fibanocci series it begins to make sense. He also uses loads of tritones. So, so clever. Worth a listen for any composer.
It was originally performed by Bartok and his wife Ditta in Basle. Blimey, they both must have been good! Imagine living in their house!