Another interesting approach for sound modification offered by the Synclavier was called ReSynthesis.
I think ReSynthesis struck the computer musicians of the day, like myself, as more interesting and useful than it struck traditional composers and production personnel.
In brief: Using ReSynthesis, up to 96 individual sampled instruments –each with their own envelope– could be sequenced by triggering a single key stroke. So for instance, a single sound could start out with a trumpet attack, transition into a violin down stroke, then into a child's laugh, then into a car horn, etc - up to 96 such changes, if one so desired.
The same thing can of course be done today by cross fading through a series of samples, but in 1987 it was a mind boggling concept.