As you look through the entries and listings of Chopin’s keyboard works on these pages, you may run into this funny “KK” designation, particularly in the early recitals.   It stands for the Kobylanska Katalog, and it’s assigned to works by Chopin that don’t have opus numbers.    It’s named after Polish musicologist (and former Curator of the Fryderyk Chopin Society Museum in Warsaw) Krystyna Kobylańska, who in 1979 authored Frédéric Chopin: Thematisch-bibliographisches Werkverzeichnis.  It is in essence a complete (and definitive) thematic catalogue of all the works by the Polish piano master – not unlike what Ludwig Koechel did for Mozart in the 19th century.