If you have the Casio software (free download), from http://music.casio.com/e/data_ex2/
, you can convert a 'midi' file that you make with the wk 1300, into the wk-3x00 format. You also need to download the manual...to get the 'how to' instructions. It's not an easy task..but can be done.
Our other user forum, http://www.originalz.com/casio/casio_bbs/
has downloads, and links to hundreds of rhythms (we converted a bunch of Roland rhythms). Also, check out http://www.casio-europe.com/euro/emi/cms/wk3500/
for more downloads.