Free for Win/Mac LoopJam https://loopjam.wordpress.com/
just load a "stereo" 4 or 8 bar section of realtrack and rearrange it just how you like by selecting a Scene number and edit it by moving the white notes up or down, then export to wav.
In BB or RB you can highlight the bars then drag to DROP WAV
you will have to convert any mono files to stereo.
*It also needs lower case .wav