When you're changing the amplitude of a sound, if the amplitude is changed very suddenly and significantly, it may create a sudden discontinuity in the waveform which will be heard as a high-frequency click. (That phenomenon is demonstrated in the example "Click resulting from amplitude change".) To avoid that problem, it's necessary to interpolate sample-by-sample from the old amplitude value to the new value, over some small period of time, to create a slightly more gentle fade to the new amplitude factor.
The example demonstrates two methods. This first one uses smoothing to create a ramp on and off instead of an instantaneous switch on and off. This second one waits a certain amount of time before it begins the release ramp, and if the input signal goes back above the threshold during that time it cancels the release (the default amplitude threshold being -40 dB).
Given a hypothetical grand master fader that can be controller with the continuous controller 13 (assuming for the sake of this example that your device is also set to receive on MIDI channel 1), you can send the message 176 13 127 to a midiout object to turn the fader up to full. Another way to do this would be to use a ctlout object, send the number 1 in the right inlet, the number 13 in the middle inlet, and then send 127 in the left inlet.