Definition and background:
The science of musical instruments including their classification and development throughout history and cultures as well as the technical study of how they produce sound. The Hornbostel-Sachs system of musical instrument classification is probably the best-known system in use today.See also Musicology; Ethnomusicology; Hornbostel-Sachs; Erich Moritz von Hornbostel; Curt Sachs.
For more information on the music term "Organology" check out these other resources:
Wikipedia - Glossary of Musical Terminology
Virginia Tech Multimedia Music Dictionary
ORB -- Medieval Music Glossary