Equipment

Synthesizers : modern digital synthesizer era

Most modern synthesizers are now completely digital, including those which model analog synthesis using digital techniques. Digital synthesizers use digital signal processing (DSP) techniques to make musical sounds. Some digital synthesizers now exist in the form of 'softsynth' software that synthesizes sound using conventional PC hardware. Others use specialized DSP hardware.

Digital synthesis

Digital synthesizers generate a digital sample, corresponding to a sound pressure, at a given sampling frequency (typically 44100 samples per second). In the most basic case, each digital oscillator is modelled by a counter. For each sample, the counter of each oscillator is advanced by an amount that varies depending on the frequency of the oscillator. For harmonic oscillators, the counter indexes a table containing the oscillator's waveform. For random-noise oscillators, the most significant bits index a table of random numbers. The values indexed by each oscillator's counter are mixed, processed, and then sent to a digital-to-analog converter, followed by an analog amplifier.

To eliminate the difficult multiplication step in the envelope generation and mixing, some synthesizers perform all of the above operations in a logarithmic coding, and add the current ADSR and mix levels to the logarithmic value of the oscillator, to effectively multiply it. To add the values in the last step of mixing, they are converted to linear values.

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