Late response to a thread that started three months ago, but...

I've created SFZ files using a Reaper to render other instruments at various velocities. It's tedious, but definitely works.

I'm not sure how well that's going to work for the OP, though. Unless you set up the opcodes on the instrument so it crossfades to another sample as the amplitude changes, it's going to to keep playing the initially triggered sample.

That means if the instrument starts a note at a low velocity, it'll trigger the sample assigned to that low velocity. As the amplitude of the same note increases, it'll continue to play that low velocity sample, but at a louder volume. That makes for a not very convincing change of dynamics.

I built some instruments for my EWI before I had the full version of Kontakt, and had exactly that problem. All the notes triggered low velocity samples, because the attack started at a low velocity.

The short term workaround was to drop the multi-velocity samples and instead use instruments sampled at one medium velocity. The long term solution was to get Kontakt and instruments that responded to varying breath pressure.

-- David Cuny
My virtual singer development blog

Vocal control, you say. Never heard of it. Is that some kind of ProTools thing?