Xiosynth's "Piano" LFO Shapes

[cartesia]

Just wondering if anyone knows the correct way to apply the 'piano' LFO shapes..

It's definitely meant to be used in one-shot mode , I'm wondering about what it should be modulating though -

Is it for a piano-like volume envelope, or should it be applied to the filter (and which gives the best result?)? Also should it be set to unipolar? and which speed is the 'correct' one (at high speed it creates a kind of 'clicky' attack effect, but at the lower speeds it sounds kinda like the duunnnnnclunk of a piano key.. vaguely.

Unfortunately the manual doesn't seem to mention it's use.