If I'm understanding what you're saying that makes sense. That is you are hearing both the sounds from your BIAB sound source and from the 81Z right? If that's the case, it has to do with what channels you have the 81Z setup to respond to. By default, BIAB outputs as follows:

Channel 2 - Bass
Channel 3 - Piano
Channel 4 - Melody
Channel 5 - Thru
Channel 6 - Strings
Channel 7 - Guitar
Channel 8 - Soloist
Channel 10 - Drums

What channel do you have the 81Z setup to respond to?

Also, are you using a MIDI interface...not an audio interface but a MIDI interface?

Jeff


Win11, Intel i7 7700K 4.2Ghz, 32Gb RAM, 2x1Tb HD, 500Gb NVMe, BIAB/RB 2025, MOTU 828MK3 audio, MOTU Midi Express, Yamaha Montage 7, DX7II, TX802, Motif XS Rack, Roland Fantom XR Rack, Oberheim Matrix 1000, VoiceLive3 Extreme, Kontakt 6, SampleTank 4.3