ADSRks

ADSRks is a term used in electronic music synthesis to describe an envelope generator that extends the traditional ADSR (Attack, Decay, Sustain, Release) envelope by incorporating keyboard scaling (KS). In ADSRks, the envelope parameters can vary depending on the played note, enabling per-note shaping of the amplitude envelope beyond a fixed, single ADSR curve.

How it works

ADSRks ties envelope behavior to the keyboard position, typically via the MIDI note number. A function maps the note value to one or more envelope parameters, such as attack time, decay time, sustain level, and release time. The result is that different keys produce slightly different envelope contours. A KS amount control often determines the strength of this variation, with options for linear, exponential, or custom curves. Some implementations apply KS to all four stages, while others target only specific stages (for example, faster attacks on higher notes).

Implementation considerations

ADSRks is commonly implemented per voice in digital synthesizers, meaning each note generates its own envelope whose parameters are adjusted by the KS function. Designers may allow selective targeting of parameters and provide presets or curves to suit different timbres. The approach can increase expressive potential, particularly in percussive or plucky sounds, pads with evolving dynamics, or keyboard-followed dynamics in subtractive or virtual-analog synthesis.

Applications and limitations

ADSRks is used to add per-note expressivity, enabling brighter or sharper onsets for higher notes or deeper, longer envelopes for lower notes. It can complicate patch design and require careful calibration to maintain consistency across the keyboard. As with any per-note modulation, computational overhead increases with the number of voices.

See also

ADSR, keyboard tracking, envelope generator, expressivity in synthesis.