Electronic musical instrument

An electronic musical instrument is any musical instrument that produces or modifies sounds by means of electronics. Instruments such as the electric guitar that generate sound by acoustic or mechanical means but that amplify the sound electrically or electronically are also considered electronic instruments.

The broad familiy of musical instruments can be classified using many systems, including Hornbastel-Sachs. Within this system, most electronic instruments, such as theremins, organs, keyboard synthesizers, and drum machines could be considered Electrophones, specifically, of type "53. Radioelectric instruments: instruments in which sound is produced by electrical means"

Broadly the gear that synth DIY is concerned with are synthesizers (analog and digital) and samplers, sequencers, drum machines, effects as well as ancillary equipment such as controllers (and protocols), amplifiers, mixers, as well as with repairing and modifying these.