information:extraction, structural:expansion, stylistic:tone, quality:correction, linguistic:paraphrasing
Classification

In musicology, electronic musical instruments are known as electrophones. Electrophones are the fifth category of musical instrument under the Hornbostel-Sachs system. Musicologists typically only classify music as electrophones if the sound is initially produced by electricity, excluding electronically controlled acoustic instruments such as pipe organs and amplified instruments such as electric guitars.

The category was added to the Hornbostel-Sachs musical instrument classification system by Sachs in 1940, in his 1940 book The History of Musical Instruments; the original 1914 version of the system did not include it. Sachs divided electrophones into three subcategories:

The last category included instruments such as theremins or synthesizers, which he called radioelectric instruments.

Francis William Galpin provided such a group in his own classification system, which is closer to Mahillon than Sachs-Hornbostel. For example, in Galpin's 1937 book A Textbook of European Musical Instruments, he lists electrophones with three second-level divisions for sound generation ("by oscillation", "electro-magnetic", and "electro-static"), as well as third-level and fourth-level categories based on the control method.

Present-day ethnomusicologists, such as Margaret Kartomi and Terry Ellingson, suggest that, in keeping with the spirit of the original Hornbostel Sachs classification scheme, if one categorizes instruments by what first produces the initial sound in the instrument, that only subcategory 53 should remain in the electrophones category. Thus, it has been more recently proposed, for example, that the pipe organ (even if it uses electric key action to control solenoid valves) remain in the aerophones category, and that the electric guitar remain in the chordophones category, and so on.