If you only use the bank 0 1 and 10, the SD2 and SD4 are the same.

SD4 have some more internal and user presets that the SD2 don't have. SD2 is like SD4 in MID mode only.

With the vArranger software, you can add auto-accompaniment features to a SD2 or SD4, playing Ketron and Yamaha styles.
_________________________
Regards,

Dan
https://www.varranger.com