Digital Synthesizers
Analog synthesizers actually date back to the 1920s, but the best-known analog synth was developed by Dr. Robert Moog in the 1960s.
In the 1970s Hal Alles of Bell Labs developed the experimental Alles Machine, known as “Alice” with 72 computer controlled oscillators.
In 1981 Yamaha introduced the GS-1 FM digital synthesizer and the in 1983, the much more commercially successful DX7. Both used digital frequency modulation tone generators to produce the sounds. They were called digital operators (as opposed to oscillators). The Yamaha synths were based on the research of Dr. John Chowning of Stanford University, and were a vast improvement over analog synths in creating sounds with complex and percussive attacks.
Around 1987 Roland introduced their D50. This was a hybrid synth, using analog synthesis with digital samples. Based on research that showed people identified sounds primarily by the information in the attack portion of the waveform, this synth used actual digital samples for the attack and analog tone generation for the sustain and decay portions.
About the same time companies like Fairlight, New England Digital, and Kurzweil developed sampling synths that used multiple digital samples of real instruments. For example, every note of a piano could be sampled at several levels of touch, from lightly hitting the key to really clobbering it. As the electronic musician played, the keyboard would sense the velocity and play the appropriate sample. This enabled these synths to sound more like the actual instruments they were emulating than ever before.