General books on instruments are at ML460 in Reference and General Stacks. Encyclopedias also have articles on instruments.
Dictionaries of instruments are in Reference at ML 102 .I5. Some of the best are:
Musical Instruments of the World by 
A Survey of Musical Instruments by 
Evert Collier's Self-Portrait with a Vanitas Still-life, 1684 (courtesy Wikimedia Commons)