From Oct 95 issue

The FM guide to FM

Frequency Modulation involves taking a sine wave and modulating its pitch with another oscillator that vibrates above a certain frequency. The result is a new, complex tone. Professor John Chowning at Stanford University had been researching this as a means of sound synthesis in the 1970s, but the computing power required was prohibitive. Enter Yamaha, who invested mega-Yen in the project. The first keyboards were expensive and stylish piano instruments, the GS-1 and GS-2; the second series, which used integrated chips, were the DXs.