Thanks for the reply - I realized after posting that it was to the Windows thread instead of the MAC, but the problem is happening with both versions. The AIFF files were done with the MAC, but using a cable called j5Create JUC400 "wormhole switch" USB, I can drag the folders with the track files one folder at a time, from the MAC HDD to the Windows computer HDD. If I "import" that folder to the MC20 WINDOWS, and use the "tag" option, when I drag a second folder the same way, it adds without mixing it with the first file. I was hoping for a fix action that would allow to import the whole library, as 600+ discs one-at-a-time is laborious. I have done an MD5 CRC check on several files before and after dragging from the MAC to the PC, and the compare is always the same, and I can't hear any difference. A basic problem is I don't understand the MAC file system very well. I have no idea how the "metadata" is embedded; the CD rips and the LP rips both look the same re track numbers and titles in a sub folder - seems to me the subfolder with the individual tracks should stay with the higher folder they're a subset of. I have found previously that if I import a lot of these and then, after having put the titles and artist in the "tag" window, if I delete the library and re-import it, they all come out right. I have updated both versions to MC21, no change to the way the import is handled.