Schoenberg's appreciation, characteristically as generous as it is backhanded, brings the difficulties inherent in the notion of “Mendelssohn as progressive” into clear focus. On the one hand, it can be difficult to remember that his music was ever in any significant way “new.” “Progressive” more readily conjures up Wagnerian forays into the uncharted realms of the music of the future than the cultivation of the familiar, if daunting, confines of the past. Mendelssohn, however – alone among composers between Beethoven and Brahms – achieved his most characteristic and personal expression in sonata-form works, while, as Charles Rosen has observed, some of his more intimate lyric utterances may “charm, but they neither provoke nor astonish.”