Originally Posted by Lazy Bird
It's normal that my configuration is not identical to yours, because my keyboard is a Clavinova CVP that produces its own sounds, and I use it both as a master keyboard AND as an expander.

That's why I don't check the VSTi/DXi synth option: with my Clavinova CVP, I don't need to use virtual instruments.

That being said, I still have the same problem when I check the VSTi/DXi option and use my virtual instruments (for example Garritan JABB 3): when I play on my keyboard with the MIDI Input Driver enabled, Band-in-a-Box stutters (stops, resumes, etc.).

For now, I have no leads!

OK, I better understand what you are trying to do. However, my understanding is the BIAB has never done that. Over the years there have been discussion about using external sounds from accompaniment keyboards and it was concluded this did not work. Only midi-in from controller keyboards using the internal BIAB synths (not VSTis) with the thru box enabled (as Andrew said in his post) and as I have configured.
But if you say what you are trying to do did work in prior versions, and now does not work in current version I can only refer you to Andrew and the PGM team. Good luck. By the way I did look up the Clavinova and it looks way cool - but way more than my stiff fingers could play. grin

BIAB – 2025, Reaper (current), i7-12700F Processor, 32GB DDR4-3200MHz RAM, 1TB WD Black NVMe SSD, 2TB WDC Blue SSD, 1TB WD Blue, 2 TB SK NVMe, 6 TB External, Motu Audio Express 6x6