You can use a Midi to USB cable, but beware though, I have one which is a few years old and I recently found it wasn’t supported on my latest OS (Mavericks) so check that it’s supported before buying. Also, I suspect cheapo interface wires may have substandard drivers and/or bad connectors, so you should be prepared for problems… I recently bought the M-Audio MidiSport 2x2 Anniversary Edition for my Mac just to make sure Midi worked reliably, and it does.
Mike.