This revised edition was prepared with reference to all manuscript sources that could be found: the sketch, final (engraving) copy, a corrected proof of the first printed edition and some communications between the composer and his publisher. Since there were several editions already in the composer's lifetime, which provided opportunities for changes and corrections, the present revised edition differs from the preceding one in only a few respects. The changes include dynamics and accents; precise endings of crescendos have been adjusted. Not a single wrong note could be found. (Peter Bartók, taken from the preface)