I think that a good suggestion might be to go and buy a book on midi. Once you understand Midi it opens up the whole world for you.

Midi is basically just a string of information, it has no sound, and makes no music by itself.
Midi consist of infomation like what note to play, what velocity to play that note, when to play it and when to stop. There are many other options but that is what it does. Now to hear music you need to send that infromation to a sample player or Synthesizer. Which has either a sample sound patch or a synthesized sound set.

Midi can be setup in several formats, GM GS, XG, these are examples of lists of sound patches or instrument patches. All of these have basically the same instrument patches, but might have a few variables.

Different synthesizers will use what is called a patch map, these are a detailed routing instructions so that the midi data will find the correct patch or sound sample for that specific synth. For instance a Roland Patch map may direct the data to a different number than say a Korg map will. What could happen if you have a roalnd synth, and are using a Standard GM patch map you might not hear a Grand piano, but a Rhodes instead.

Channels are paths that the midi data takes from one device to another. For instance you have 3 midi tracks inside Real Band, and you want to send the data in those tracks to a Roland keyboard to play all three instrument sounds. So that they play properly you need to send each separate track on a separate Midi channel, maybe Piano on channel 1, Bass on Channel 2, Strings on Channel 3. Or what ever, as long as they are not sending on the same channel.

So if you are using a Roland synth to create the sound, you need to setup either BiaB or RB so that it sends midi data out on assigned channels, using a roland patch map, or a Standard GM map if your synth has that capability.

HP Win 11 12 gig ram, Mac mini Sonoma with 16 gig of ram, BiaB/RB 2026, Reaper 7, Harrison Mixbus 11 , Presonus Audiobox USB96