If you set up a release sample layer in gigastudio, the samples get triggered when the key releases UNLESS the sustain pedal had been depressed before the note was played. Releasing the sustain pedal would hopefully trigger the release samples for all notes being sustained, but it does not. This makes sampled reverb tail releases pretty useless( unless one doen't use the sustain pedal ).
Gigastudio 3 has a new release trigger feature, but I'm not sure how this would be used to get a dimension of release samples to fire on pedal up. There is an example in the doc showing how to set this up for a highhat effect. I'm not sure how one would use it, however, for something like a harpsichord release, or reverb tails.