Volume IX of the Transactions on Rough Sets (TRS) provides evidence of the continuing growth of a number of research streams that were either directly or indirectly begun by the seminal work on rough sets by Zdzis law Pawlak (1926- 1 2006) .OneoftheseresearchstreamsinspiredbyProf.Pawlakisroughset-based intelligent systems, a topic that was an important part of his early 1970s work on knowledge description systems prior to his discovery of rough sets during the early 1980s. Evidence of intelligent systems as a recurring motif over the past twodecadescanbefoundintherough-setliteraturethatnowincludesover4,000 2 publications by more than 1,600 authors in the rough set database . This volume of the TRS includes articles that are extensions of papers in- 3 cludedinthe?rstconferenceonRoughSetsandIntelligentSystemsParadigms . In addition to research on intelligent systems, this volume also presents papers that re?ect the profound in?uence of a number of other research initiatives by Zdzis law Pawlak. In particular, this volume introduces a number of new advances in the fo- dations and applications of arti?cial intelligence, engineering, image processing, logic, mathematics, medicine, music, and science. These advances have sign- icant implications in a number of research areas such as attribute reduction, approximation schemes, category-based inductive reasoning, classi?ers, classi- ing mappings, context algebras, data mining, decision attributes, decision rules, decision support, diagnostic feature analysis, EEG classi?cation, feature ana- sis, granular computing, hierarchical classi?ers, indiscernibility relations, inf- mationgranulation,informationsystems,musicalrhythm retrieval,probabilistic dependencies, reducts, rough-fuzzy C-means, rough inclusion functions, rou- ness, singing voice recognition, and vagueness. A total of 47 researchers are represented in this volume.