Pin 5 on the arduino is connected to an IC on the ns1 already. I was super confused by that too until I checked the schematic. I just don’t use pin 5 in my arduino firmware. I haven’t used the midi implementation, but it looks like it’d be not too difficult to change the pin to another unused digital pin.
I’m not %100 positive, but i think it is safer to go with the higher pins because they arent connected to other ICs.
I think pin 5 was for a dac or something? Little thing has so many things to play with 0.o