A couple of things Big John, we need a lot more information in order to help. Things like what MIDI player, how are you using it with BiaB and what DAW are you using. Are you downloading GM MIDI files from the Internet and playing them? Are you adding parts to a MIDI file in BiaB? Things like this need to be explained so we can help.

Also RTs are audio files and they can not be played on a MIDI player. MIDI is data only and that data tells the player/BiaB what General MIDI (GM) sound to play and in some cases how to play it. BiaB and your MIDI player have GM sound sources built into them. In BiaB's case you can change the included GM sound source to a better one.

I hope this helps.

My wife had her driving test today.
She got 8 out of 10.
The other 2 jumped out of the way!

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware