The informal manual to use the ARA plugin is very useful… but a bit confusing. Looking at instructions to use with Reaper, depending on the section of the document, you can apply the plugin to an audio track (item FX) or to the whole track (track FX). BOTH WAYS DO WORK.
But I noticed that when using multiple Synth-V tracks in the plugin, if the plugin is added to ITEMS (audio clips), SOMETIMES there are terrible sync problems. Audio is stuttering (when my computer is well below 5% CPU). You can see the transport cursor movin irregularly, like trembling, even backwards.
I noticed this can be triggered if I add effects (say a reverb or a basic EQ) to one of the tracks. Putting the track one level below does NOT help. Putting the effects in a parent track that includes all voices sing Synth-V does help… but this means same effects for all the voices.
To make things worse this “stuttering” is triggered very randomly. I once managed to add FX to tracks without issues. I saved the project (to be a template). Next time I opened it it was stuttering again.
This NEVER happens if I add the ARA plugin at track level. It works as supposed. No stuttering at all. In fact, Synth-V “pre-renders” all tracks, so my system is possibly OK up to >100 Synth-V tracks.
ARA management looks really complex to me, I don’t really know if this bug is inside Reaper or Synth-V, In fact I think that full ARA support is relatively new in Reaper, and I’ve never used an ARA plugin before.
My solution is to only use ARA plugin as track FX (not item), but this way I cannot copy clips (“groups” inside Synth-V), which is limiting today. (described in ARA Synthesizer V Studio 1.11.0b3: Copy & Paste GROUPS).
To me the best solution would be to use the ARA plugin in Reaper as track FX and add the “paste group” feature. It also looks the simplest to solve (no dependence on Reaper).