AN OVERVIEW OF THE MAIN INSTRUMENT SAMPLElibraries used in psychoacoustics, sound analysis, and instrument classification research is presented. One of the central libraries, the McGill University Master Samples (MUMS, Opolko & Wapnick, 2006) is reviewed in detail. This library has over 6000 sound samples representing most classical and popular musical instruments and a wide variety of articulation styles. A closer scrutiny revealed a conspicuous amount of labeling errors, intonation inaccuracies, and the absence of an integrated database. These errors are identified and catalogued, and revisions are implemented in a form of an installer.