You are probably appending your tunes to the current playset. When title search page is displayed, is the word 'Search' or 'Append' in the upper left corner? You can change it by 'Select mode' on Rio remote (and 'CD-MD-CH', IIRC, on Kenwood one).

Dragi "Bonzi" Raos
Zagreb, Croatia
Q#5196, MkII#80000376, 18GB green