Someone else would probably be able to help you more with this.

I believe you don't have to invert the data. (I know that you don't have to invert the data when sending midi out from a pic, so I'm assuming you don't have to invert the data when receiving as well.)

(There are some old diagrams on the web that show the need for using a 7404 hex inverter chip to properly send midi data out of the pic. It was later found that the PIC does not need this extra inverter chip to send midi out. Because it can send non-inverted serial data. I've never inverted the signal when making midi controllers (sending midi)).