Ullman's seven Piano Sonatas were written between 1936 and 1944. Though rediscovered as recently as 1990, they are now available in a number of recordings. Neo-classical in approach, the piano writing and the use of polytonality places them closer to Skriabin and Prokofiev than to the works of Ullman's teachers Arnold Schoenberg and Alois Hába - this applies also to the Piano Concerto, written during the same period. The numerous quotes from Mozart, Wagner, Mahler, and Dukas to folksongs and tunes from operettas are particulary interesting in this context.