<Li> electrophones, such as the electric guitar or electric bass, which produce sound through electricity and is required to be plugged into an amplifier . </Li> <P> In the Hornbostel - Sachs classification of musical instruments, lamellophones are considered plucked idiophones, a category that includes various forms of jaw harp and the European mechanical music box, as well as the huge variety of African and Afro - Latin thumb pianos such as the mbira and marimbula . </P> <P> Later Sachs added a fifth category, electrophones, such as theremins, which produce sound by electronic means . Modern synthesizers and electronic instruments fall in this category . Within each category are many subgroups . The system has been criticised and revised over the years, but remains widely used by ethnomusicologists and organologists . </P> <P> In 1932, comparative musicologist (ethnomusicologist) André Schaeffner developed a new classification scheme that was "exhaustive, potentially covering all real and conceivable instruments". </P>

What category of instruments do synthesizers fall in