My guess is that you need to start with just one relay at a time. Hook up your ins ground Vcc and in1 should be your midi output signal, to create that signal you will need your code to signal a message to turn on in1. Showing your code would definitely help. but usually in midi the basic is that an input trigger with a 10k resister to an analog input will send a message. but this is all very general info, you can also use the digital inputs it all depends on your code, also notice the the 3 outputs of each relay one is always closed and one is always open and closed only when activated. so post your code you should get more help and your schematic if you can, if you haven't found it already there's a free product called fritzing easily found on Google to help you build circuits using actual parts, and then creates a schematic for you, and will even allow you to pay them to make you a pcb board, which i here is pretty good quality, but its a nice program, if you don't have it, I believe its cross platform and its opensource. Hope I may have helped a little, and with some more info, im sure some one with more experience will help, good luck!