1965: Robert Moog invents Moog Synthesizer using analog technology, which manipulates sine waves.
1968: Walter Carlos produces hit album ``Switched-On Bach,'' featuring classical music played on Moog Synthesizer.
1969: Introduction of Minimoog, first portable keyboard to be sold by musical instrument retailers.
1975: Oberheim Electronics produces first commercially available polyphonic synthesizer (can play more than one note at a time).
Early '80s: Digital synthesizers with inexpensive microprocessors available. ``Sampling,'' or the ability to make short digital recordings and play them back at any pitch, introduced.
1983: Manufacturers standardize keyboards with MIDI (Musical Instrument Digital Interface), allowing compatibility. The Yamaha DX7, a powerful and inexpensive keyboard, sells over 200,000 units.
1983-present: MIDI spurs creation of new electronic instruments. Personal computers widely used to store and edit music.
1989: Maturing of synthesizer market contributes to 12 percent decrease in units shipped to retailers, according to American Music Conference.