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In recent years, digital synthesis has become the dominant technology for electronic music. The heart of this development is the digital-to-analog converter (DAC), which produces a voltage proportional to a given digital input. A steady stream of input values (usually called samples) to the DAC will generate a time-varying voltage that can be amplified and used to drive a loudspeaker.
The DAC converts some constant number of samples per second, called the ``sampling rate.'' Nyquist showed that the highest frequency a DAC can produce is half its sampling rate. Since the upper frequency limit of human hearing is around 22kHz, sampling rates for digital audio are approximately 40kHz. Assuming one collects stereo, 16 bit samples at 40kHz, ten minutes of sound will require nearly 100 million bytes worth of samples. The challenge of digital audio is to find efficient ways to control and generate these millions of samples.