The Systems Concepts Digital Synthesizer is a large (2500 integrated circuits), powerful (20 million multiplications per second) machine designed to synthesize complex musical pieces in real time. To accomplish this, it has several computational elements which operate simultaneously. The requirement of real-time synthesis necessitates special-purpose structures in the architecture of the Synthesizer, as well as general-purpose ones. Since the Synthesizer was put in service at the Stanford University Center for Computer Research in Music and Acoustics, it has received intensive use by many composers, employing a wide variety of musical idioms. Illustrative excerpts are presented.