adsr~

The adsr~ object provides a signal in the shape of an ADSR envelope (attack, decay, sustain, release) commonly used in synthesizer design. You specify an attack time in ms (time to get from 0 amplitude to peak amplitude), a decay time in ms (time to settle to the sustain level), a sustain level (an amplitude factor, not a ms time), and a release time in ms (time to return to 0). Those values can all be supplied as initializing arguments, and/or as floats or signals in the second, third, fourth, and fifth inlets.

An ADSR envelope generator is a common tool for controlling the amplitude of a note, and in fact it can be used to control any parameter of a sound. In this example, one adsr~ object controls the amplitude of a note while another adsr~ controls the cutoff frequency of a lowpass filter on the sound. Both are triggered at the same moment, but they have slightly different parameters for independent envelope shapes.

The way that a sound’s amplitude evolves over time is called its amplitude envelope.

This shows an implementation of phase distortion synthesis in MSP—using the phasor~, kink~, and cycle~ objects—in a patch that is designed to be used inside the poly~ object. For an explanation of this sort of phase distortion synthesis, see “A demonstration of phase distortion synthesis.” The main point of this example, though, is to show how a synthesis patch can be designed to respond directly to MIDI input.

This patch demonstrates how one might make an audio patch that can serve as a voice in a polyphonic synthesizer. It's quite similar to the FMtone~ patch shown in “Generating a simple 2-operator FM tone”, but with some modifications that make it suitable for use with the poly~ object so that it can be used polyphonically.

In order to enable and disable portions of an audio program easily, and to be able to reuse them multiple times, you will probably want to encapsulate an entire audio-generating or audio-processing procedure inside a single patch with inlets and outlets so that it can be used as a subpatch object in some other patch. This patch shows an example of a simple 2-oscillator frequency modulation tone generator that could easily be used as a subpatch in some other patch.