This is a very, very convenient "splitter" for MIDI messages – called MIDI interface/patcher in music lingo. Usually one can daisy chain all of the availalbe MIDI gear and configure each box to respond only to its assigned channels (major hassle, believe me – I suffered for full 6 years!). The Edirol UM-880 allows each MIDI device to have all 16 channels for itself. It sounds deceptively simple, but in reality there are good reasons for these beasts to exist.