Sonatas'' (beside the ballades, scherzos and the ''Fantasia in F minor'') form a group of works from the period of synthesis, characterised by masterly technique and themost intense expression. Volume X of the National Edition contains two ''Sonatas'' by Chopin. Of the variants in musical notation, those designated ''ossia'' were marked inthis way by Chopin himself or inscribed in his hand in his pupils' copies, while those without this indication result from textual divergences in authentic copies or fromdifficulties in reading the text in an unambiguous way.