When was the synthesizer keyboard invented?
Synthesizer
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One of the earliest electric musical instruments, the Musical Telegraph, was invented in 1876 by American electrical engineer Elisha Gray. He accidentally discovered the sound generation from a self-vibrating electromechanical circuit, and invented a basic single-note oscillator. This instrument used steel reeds with oscillations created by electromagnets transmitted over a telegraph line.  Gray also built a simple loudspeaker device into later models, consisting of a vibrating diaphragm in a magnetic field, to make the oscillator audible.[3][4] This instrument was a remote electromechanical musical instrument that used telegraphy and electric buzzers that generated fixed timbre sound. Though it lacked an arbitrary sound-synthesis function, some have erroneously called it the first synthesizer.[1][2]