I have the SP-2 pedal connected to my WK-500 and it does work. However, the sustain doesn't work until the pedal is depressed almost all the way down, about a half inch from the bottom (then the sustain-on indicator shows on the display). I don't like that. I don't know if this has to do with half-pedal capability, which the WK-500 doesn't support. My sister bought a On Stage KSP100 pedal for her cheaper Casio keyboard and it registers much quicker in my opinion, when the pedal is pressed about a quarter of the way down.