Hi,
Just sharing.
Dont think that the usb would be a problem. You need to setup the sy77 to recieve sysex.
1. Press UTILITY.
2. Press F2 (MIDI).
3. Select Channel Set and press the ENTER key.
4. Set Voice Recv Ch = omn.
5. Set Bulk Protect = off.
For older keyboard try to set the buffer for the sysex library to be lower (128 bytes?). Try Midi OX