A sequence of piano sonatas offers one of the most direct looks into a composer's most private and most practical obsessions, not to mention one easy way to measure the evolution (or lack of evolution) of their compositional techniques. Mozart, Haydn, Beethoven, and Schubert turned them out by the dozen. The romantics were much more cautious, with Chopin, Brahms, Schumann writing only three apiece. In the 20th century, certain Russians regained ground in terms of sheer numbers, such as Mednter (14), Scriabin (10), Prokofiev (9) and Ustvolskaya (6). As for some prominent Americans, Copland, Carter and Barber wrote one, Ives wrote two, Sessions three and Wuorinen four. George Walker is one of the few leading American composers of the 20th century to produce as many as five piano sonatas. Taken together, they securely chart a lifetime of stylistic change. Walker managed many other feats, a number of them connected to being the first black person to break through various glass ceilings: the first to be accepted at the Curtis Institute of Music, first to study with Nadia Boulanger and the first to win the Pulitzer Prize in Music. Walker is also one of the only major composer-pianists to have recorded worthy performances of virtuoso standard repertoire including Beethoven's "Emperor Concerto" and the Brahms second piano concerto.