This is exactly what I have been searching for also. Since realizing how fast an SD card is when hooked to our CVP 307 at church through the USB port and also how massively much more storage is available than a paltry little floppy, I began lusting to do the same thing with my PSR 740.
The good news is there's a device available that is supposed to do that. The bad news is they want $275 for it! The worse news is that a techie friend reminded me that no matter what magic black box they put in between the floppy interface and USB interface, it will never transfer data any faster than the old floppy rate which as we all know is pathetic. It will improve some if you use a solid state memory like flash memory as there are no moving parts which need to get up to speed and seek before reading and writing but nothing approaching USB speeds. I have abandoned that quest and now aspire to earn enough money to buy a more modern keyboard and chalk it up to technological advancement more than planned obsolescence.
