Cover the debugging incrementally:-
1. Put a printf statement in (that shows the code block with midisend_str() is reached)
2. Put in midisend() in addition (that shows the code, midi channel and Midi-OX working together as expected for 3 byte midi output)
Then
3. Puzzle at the new midisend_str(). But at least the OSCII-bot process hasn't crashed like Celphor