Three folders. Is this possible?

[Wixter]

I have a folder on my computer containing all my hi-res music files.

I also have a micro SD card which contains some of those files because all of them will not fit.

I would like to insert a new SD card into my card reader and copy from the computer to the new SD card only those files not on the first SD card.

Any way to do this? I have the "pro" variant of BC4

[Chris]

Beyond Compare can't do a three folder comparison. However, there is a workaround using a snapshot.

Run Beyond Compare.
Copy files from your computer to SD card 1.
Use Tools > Save Snapshot to save a directory listing of the files on SD card 1.
Load a comparison of your computer's music folder and the snapshot of SD card 1 in the Folder Compare.
Select orphan files in the computer music folder.
Actions > Copy to Folder, then specify SD card 2 as the target.