What is the difference between the Yamaha ypg525 and ypg535?

Answer 1

usually the difference is more sounds, probably more or less midi connections, maybe a floppy drive was added onto it, etc. if the numbers are a little bit higher than the other, not TOO much has been done, usually. if it were a bigger gap of number, or a higher set of letters from the alphabet, much much more is done, it'll be practically a whole new keyboard. more keys, more sounds, different color, bigger speakers. etc