The composite RCA video output delivers the score and lyric display (or simply mirrors the internal display) to an external monitor. - See more at: http://www.korg.com/us/products/synthesizers/pa4x/page_2.php#sthash.Lpngr3eF.dpuf

If you use the video out, you can display lyrics and score on an external screen while leaving the kb screen for normal use. Or you can choose to have it mirror the internal screen.