Reply to Connecting S4 & S2 together?

A friend and I are going to start doing some gigs together. I have an S4 and he has an S2. Went over to his house to practice and was going to plug a MIDI cable from mine to his, but realized the S2 has no MIDI ports.

So what is the best way for us to sync up? Should he buy a USB MIDI device? Would that even work?

Let me know your thoughts.

Thanks!