Turns out that he is working on composing the music of a French TV series in Logic Pro X and needed a way to reproduce the midi signal of channel 1 to all the other channels from 2 to 16. And Logic Pro gently gave him a text editor to write code in!
For programmers, this is quite straigthforward, but for my brother, it was like the graal. He told me that he lost 3 hours on the Internet searching if someone had already done this, and just found a guy selling a bunch of scripts for 40 bucks. Well, I guess musicians will need their stackoverflow quite soon.