Welcome to the forum.

RealTracks cannot be used to play exact MIDI parts, if that's what you are asking.

RealTracks are pre-recorded snippets of audio performed by actual accomplished players. They follow the chords you enter into BIAB and can be made to obey certain rhythms, but will not play an imported MIDI part.

You can use your MIDI on the Melody and Soloist tracks. The other tracks can have either MIDI or RealTracks (or loops) but will be regenerated (the arrangement changed) each time you press Gen/Play.

If you want to use MIDI on tracks other than Melody and Soloist, you CAN alter those tracks but remember to freeze them.

Or - are you asking how to select a RealTrack to play on what is now a MIDI track (knowing it will make up its own part)?

This is probably way too much information at this point; write back when you need help. Just remember the nature of audio (RealTracks) is quite different from MIDI. Each has its advantages and disadvantages.

BIAB 2025 Win Audiophile. Software: Studio One 7 Pro, Swam horns, Acoustica-7, Notion 6, Song Master Pro, Win 11 Home. Hardware: Intel i9, 32 Gb; Roland Integra-7, Presonus 192 & Faderport 8, Royer 121, Adam Sub8 & Neumann 120 monitors.