If I understand the question rightly, the only way I know how to effect audio (as opposed to MIDI) in such a way is to use a dynamics processor of some sort. I’d first reach for a transient shaper, which listens to the volume envelope of an audio signal, and these typically have a knob for attack and sustain. For a more staccato sound, I’d lower the sustain, and vice-versa. Alternatively or in addition to the former processor, I might use a gate if I wanted more silence between notes, and I might use its opposite, a compressor, to bring up lower-level sustain. None of these processes will to change a performance, however.