This is using BiabVST and ReaTrak to choose from the thousands of session players instruments and drums to add track/s to your own session.

In the demo video we are fitting a guitar solo in this case starting at bar 17 to 24, the bars were highlighted and the 7 solos generated.
To preview the solos in sync to my existing tracks I select one track at a time in the VST setting it to play along with the Reaper tracks, I do this until I find a solo that fits best then simply drag it into Reaper (it has a 1 bar buffer at each end to allow for pick-up notes and tail notes.
The yellow icons on the right are the MIDI notation (RealCharts) that can also be dragged in.

Watch
https://www.dropbox.com/s/4dqm8awxjpohn2k/BiabVST-Multiriff.mp4?dl=0

Download
https://www.dropbox.com/s/4dqm8awxjpohn2k/BiabVST-Multiriff.mp4?dl=1

Here's a list of instruments, drums and session player.
They will show in the browser if you right click open in new tab
or to download right click save target/link as

PGmusicRealTracksList2019.txt

PGmusicRealDrumsList2019.txt

Use ctrl/cmd+mouse wheel to fit to page.

 

Nice! I've been using BIAB and REALTRACKS for awhile, but I haven't made use of the VSTi plugin yet. Looks cool. Will have to get onboard with this! Thanks for the demo.

 

Very nice demo - thanks very much for posting that.

A question:
The Chords specified in the Reaper-Region/ReaTrak and the chords specified in BiaB.
Did these get mapped to each other automatically or did you have to match them up manually?
I'm just guessing automatic - but picking your brains cos you know the answer.

Aside: Just in case this is new to anyone reading this thread,
worth noting that ReaTrack for Reaper and RealTracks for BiaB are very different animals.