That's why I said about sample sets for each ReaTrack/Drum.
This way you can create whatever solo you like and it will blend in with the original instrument.
This is what UJAM instruments have, they have actual session players playing as well as a sample set of their instrument.

This is one I made to match Oliver's guitar
Free Archtop Guitar for RealTrack Jazz Electric Guitar (27)
example RealTrack playing then sample instrument
https://www.dropbox.com/s/6krkobu3yb65wsr/RealTrack-ShinyGuitar.mp4?dl=0