Universally acknowledged as one of Bartok's masterpieces, the Sonata demands intricate synchronization between the two pianos and percussion. Although the percussion often has a merely accompanimental function, adding emphasis or setting off ideas delineated by the pianos, Bartok nonetheless paid considerable attention to balancing all of the instruments. The score not only contains precise performance directions but also a drawing that shows correct instrumental placement: the pianos, keyboards facing the audience, are to be grouped on either side and in front of the percussion, with pitched instruments in closest proximity to the pianos. (In December 1940, at the instigation of his publisher, Bartok transcribed the Sonata as the Concerto for two Pianos and Orchestra, a work not often heard but of considerable interest nonetheless.)

    Bartok had perviously demonstrated a fascination for combining piano (which is, after all, essentially a percussive instrument) and percussion, most notably in the remarkable, and at that time (1926) unique, slow movement of his First Piano Concerto, scored only for piano, percussion, and winds. However, the harmonic language of the Sonata - systemized and extremely complex (as are its structural relationships) - is much less concerned with barbaric drive and percussive discord. Rather than tone-clusters, the Sonata features chords of fifths and octaves, and even simple triands, along with an overlying tonality of C major (though with tritonal emphasis). Still, the Sonata's most striking aspect - even more so than the many singular color effects - is perhaps its non-violent assymetrical rhythmic propulsion and the sheer dancelike quality of much of the music.