You can delete multiple records from the PSR-2100. However, you can easily add or delete records from your PC. The PSR Tutorial has lots of lessons on the Music Finder and they can explain how to modify Music Finder records. You will also find information on two utilities, Michae Bedesem's MusicFinderView and Fabien's Excel editor. You can save your Music Finder database to floppy; take it to your PC; load it into Music Finder View; delete and/or modify all the records you want; and then save it, perhaps under a different name. Take that back to your 2100 and load it in. Here's a direct link to the PSR Tutorial lessons on Music Finder utilities:
http://psrtutorial.com/Lessons/L_MusicFinder/MF_Util/mf_util.html