Originally posted by Jake Johnson:
ADSR settings shouldn\'t be confused with the actual time at which events occur in a sample. ADSR controls amplitude, and thus volume, remember, not time (although by changing ADSR settings, you can give the illusion of changing what happens to the length of a sample).
Actually attack, decay and release ARE rate control, i.e. they DO control time at which events occur. Only sustain is a level (relative volume) control (0-100%). Ok now, what events?
ADSR is only a relative volume attenuation \"shape\" you put on a sample. That said, the way it works in standard samples it can only be between 0% and 100% of the original recording level. You cannot increase, in a piano sample, the relative level of a given fraction of the sample because of the decaying nature of the sample itself (after the initial transients).
For example, the Decay setting doesn\'t control the length of the decay. It controls the rate at which the amplitude drops from, on a piano, the loudest part of the sample to the next level, the Sustain level. Thus, if you raise the Decay setting, the initial decay volume falls more slowly to the Sustain level, which you can also raise or lower in amplitude\\volume, so the note will sustain more loudly or softly than the sound the mic picked up when the sample was recorded.
That\'s not exactly true. You can slow down the volume fall to sustain level ONLY IF the initial Sustain setting was less that 100%. You will never be able to make the piano decay appear longer that in the actual recorded sample. But usually developers already leave the samples to their greatest sustain level (100%) so you cannot increase neither the perceived sustain neither the decay rate. Of course you can decrease them.
Also I suppose by sustain level in the piano sample you mean the part after the initial transients and harmonic development, i.e. the part of the sample where the harmonic modes do not change anymore and where the amplitude decreases slowly (and which was - and sometimes still is - usually looped). But this is actually a very slow decay, not a sustain.