In the Korg community, "F R" often stands for or "Full Real" depending on the programmer. For the Pa 80/20 series, it specifically refers to a custom sound architecture that rearranges the keyboard’s DSP (Digital Signal Processor) to handle:

: Press ENTER/YES to confirm. A progress bar will show the loading status. 3. Accessing Your New Tallava Sounds

Unlike factory styles where a fill takes 1 bar, the F R set has "stutter fills" that last only 1/8 of a bar, perfect for the stop-start dynamics of modern Tallava.