A low-frequency simple-harmonic oscillator, employing a relatively new method of approach, is described. An electronic analog computer of the differential analyzer type is used to solve the differential equation of a mass-spring system. Three dc operational amplifiers perform the computation and a sinusoidal output is obtained as the solution of the differential equation. Frequency is variable from 0.01 to 100 radians per second in steps of 0.01 radian per second. Distortion is less than 0.1 percent. Maximum output is 90 volts peak into a load of 100 000 ohms. The oscillator is particularly useful in the design and testing of servomechanisms and electronic simulators.