My recording of the complete works is based on the system of compilation applied by Dr. Ralf Wehner of the Saxon Academy of Sciences an Humanities in Leipzig. (MWV, catalogue of Mendelssohn's works)
The category MWV U lists the piano works in chronological order of their composition, opening up completely new perspectives on the way Mendelssohn worked. It is clear, for example, that Mendelssohn first wrote his fugues, then composed the preludes to them quite a bit later, in order to publish them quite a bit later, in order to publish them as pairs of Preludes and Fugues
The MWV system reveals and explains many new aspects of Mendelssohn's genius: it shows that he was borne along in a constant flow of inspiration and composition and would be working almost simutaneously at several different works, then revising them in places before publication. He spoke himself of his "revisionitis" By the sheer quantity of music he produced, 1820 and 1821 rank as anni mirabili in Felix's accelerated development. In particular, the first two bound autograph volumes of the "Berlin Nachlass" chronicle his remarkable ability to work simutaneously on unrelated compositions. Freely intermingled are biano, organ and chamber works, solo Lieder and parts-songs, sacred choral works, small dramatic scenes, and, of course, fugues. The distribution of composition is revealing. " (Larry Todd)