Margaret Birley, Keeper of Musical Instruments at the Horniman Museum writes:
There are many different classification systems for musical instruments. The classification system that is cited for musical instruments on the MIRN website is the Hornbostel Sachs system as revised by Jeremy Montagu and MIMO which is widely used by museums. However, the existence of other classification systems should be indicated. … I would suggest … Margaret Kartomi’s On Concepts and Classifications of Musical Instruments (Chicago, 1990), which provides a wide-ranging overview of musical instrument classifications.