The point is that they’re not triggered by the same key. In fact you can use different samples. Here’s a setup that works:
- program-level multi envelope set to legato (layer envelope probably works just as well)
- layer setting = mono retrigger
- multiple keygroups in same layer, with grain position modulated by the envelope
I haven’t tried it with keygroups from different layers yet… I suspect they wouldn’t work since it relies on the mono retrigger layer setting