Thanks for looking into this. Hmmm interesting. I don't think Yamaha's need checksum. Or at least the AN200 doesn't need it because I'm already controlling a load of sysex parameters for it! And I don't need checksum.
Maybe the system edit (which is the sequencer play type) needs a checksum. Hmm will try and see if this is the case!
Want it to work so much!!!!