Hi

I don’t have Reaper, but I do use Bandlabs Cakewalk.
Not certain that this is what you want to do but it works fine for me.

First I open Cakewalk on a new blank project.
This is set up to use my Coolsoft Virtual Synth and a Yamaha xg sound font for midi.
Next inset BIAB Daw as a soft synth
Open an existing BIAB MGU (all midi style and melody).in the Daw.
Important: GENERATE the song
The midi tracks for all the style and melody should now show in the Daw (bright yellow).
Now I can drag each midi track to Cakewalk and it will put them on a midi track for me. Depending on your Daw you may have to make empty midi tracks to drag to.

Now the song plays as midi via my Coolsoft synth in Cakewalk.

Have fun
Mike

BIAB2021 UltraPlus,AsusN55S1Tbssd, W10/64,Akai EIEpro
Yamaha CVP405,SquireStrat, CoolsoftVMidSynth
Novatation Impulse61 Ctr kbd, Cwalk blab Kontakt

http://mikesmusic.byethost16.com/