I have done exactly that on my MacBook Pro, where I need to preserve space somewhat. It's quite akward, though, since the RealTracks are split into several files. The audio files are the easy part. They are located in the 'RealTracks' folder, organised into separate folders with informative names, such as '/Applications/Band-in-a-Box/RealTracks/Banjo, Tenor, Rhythm DixielandFastA-B Sw 165'. The other type of files are trickier. They are corresponding Soloist files, located in the 'Soloist' folder, with somewhat cryptic names (they seem to follow the ancient DOS filename conventions, with max 8 char file names and 3 char extension), which however seem to follow a naming pattern, such as '/Applications/Band-in-a-Box/Soloists/RBanj013.ST2' and '/Applications/Band-in-a-Box/Soloists/RBanj013.XT2'.

I haven't found an easy way to pair them. What I did was the following: From my external drive (containing all RealTracks and Soloists), I copied the RealTracks folder that I wanted (mostly Jazz realtracks in my case) into the RealTracks folder on my MacBook. I then started Biab, and opened up the RealTracks picker dialog. In that dialog, there are two checkboxes 'Show RealTracks that are N/A' and 'Show Error Messages'. I checked both of them, and clicked the 'Rebuild and Fix' button. The RealTracks list in the dialogue now shows error messages for those RealTracks where the Soloist files are missing (referring to those cryptic 8+3 filenames). So I went through the list, locating the corresponding .XT2 and .ST2 files on the external drive and copied them over to the MacBook, then clicked 'Rebuild and Fix' to make sure the error messages disappeard and the Realtracks were correctly located.

Not very user-friendly, but doable (it took me a couple of hours). Is it worth it? Not if you have disk space to spare.

Good luck!

/Björn