it’s a TRS MIDI converter cable with a floating Tip like it’s used in Chase Bliss pedals. It’s really bonkers how many weird iterations there are for MIDI that itself is a 40 y old standard and you would think it’s settled. Just counted the other day 6 different version in my tiny living-room studio. Some of them can talk to others, some need a specific cable, some require converter, some more elaborate witchcraft. There also is no existing comprehensive converter translating all of them.