This demonstration produces the same sounds as in the sound synthesis demo, but uses a real-time processor, a programmable digital signal processor (DSP), in order to get higher quality sound. The sample rate used is 32,000 samples per second, four times higher than the 8,000 samples per second supported by the workstation. The processor is a Motorola DSP56002. The synthesis technique, due to John Chowning, is frequency modulation.
You may wish to refer to the introduction to the western musical scale.