For all USB-type MOTU interfaces, you will need the three FreeMidi extensions as well as the MOTU USB driver extension.For the USB Unitor 8 interface you will need the USB Unitor Family Driver version 1.0 or later.For the USB MidiSport interface you will need the USB MidiSport Shim extension.For any Opcode USB interfaces you will need the USB OMS extension.For connecting regular serial port interfaces to a Blue G3 or G4 computer, you will need a Stealthport or Gport installed into the computer's internal modem slot. No separate extensions are required for this type of connection. These interfaces include most Opcode Studio series of interfaces (3, 4, 5, 64xtc, 128x and so on) and the Unitor 8 and MidiMan interfaces.