I couldn't figure it out with Studio One, but I also don't really understand the routing in S1, so that's not saying much. Hopefully it can be fixed soon!
Bitwig works great, although there are a few different ways to do this, and some work better (for me) than others. Here's how I did it, initially:

The first track is just a virtual instrument track running the Keyscape C7. It doesn't have any native sympathetic resonance, so it's a fun one to send into Pianoteq to give it a little life.
The second track (Pianoteq FX) is an audio track, receiving input from the first track, and there's a Pianoteq insert there which you can see in the screenshot is just adding resonance within Pianoteq itself.
What I didn't like about this is that the resonance is combined with the original signal on the track. You can see this by comparing the meter in the FX Pianoteq instance to the track meters.
I'm now taking this approach, instead, and like it a lot more:

First track is the same.
Second track is still an audio track, but isn't receiving any input. The first insert is the "Audio Receiver" Bitwig device, which takes the audio from Keyscape C7 (POST). The next device, Pianoteq, provides sympathetic resonance as before. You can see the level meter for this track now matches with Pianoteq, and my resonance can be mixed independently from Keyscape.
Overall, it works well and sounds great. and I've not experienced any distortion others have reported when sliding the dry/wet or wood/strings parameters around.
Last edited by miiindbullets (09-12-2022 04:33)