John has you going to the right places.

As long as Midi is directed to your keyboard (external synth), in the "Midi/Audio Drives Setup", then anything you are hearing via your computer output is audio (i.e., Real Tracks or Real Drums). BIAB is really great at mixing audio and midi.

Oh and be sure you don't have 'Use VST/Dxi" checked in this same setup area since this will send Midi to an internal software synth and then output it via the computer output.

Sounds confusing, but once you get it, it will be a joy.

welcome to the forum from one chicago boy to another.

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