There was a time when it seemed necessary for admirers of the work of Heinrich Schenker to remind the musical community periodically that it had grown out of a lifetime of practical musical experience—that is, that Der freie Satz did not represent a self-contained system of theoretical speculation. Schenker himself tried repeatedly throughout his career to impress this point upon his readers. In recent years, fortunately, this reminder—which had threatened to become merely ritualistic—has become somewhat less necessary. The change in Schenker's reputation may, it seems, be dated precisely to 1975, when Dover Publications issued an inexpensive reprint of his landmark edition of the Beethoven piano sonatas. Since that time, increasing numbers of musicians have come to realize that Schenker was one of the founders of modern editorial practice. Those who have looked further have discovered, in addition, that he was an accomplished composer, a prolific critic, and an active performer (as a pianist and a vocal accompanist). That he was also the most influential theorist of this century is by now generally conceded, if not generally celebrated.
Rothstein, William, "Heinrich Schenker as an Interpreter of Beethoven's Piano Sonatas" (1984). CUNY Academic Works.