What is it? It has couple of tricks under it's sleeves and you can mix and blend those as you need. I'm using the midi routing capability to route midi messages from one midi source to an other one without any limitation. Sources and destinations can be USB MIDI devices, regular 5 pin MIDI equipment or even any virtual MIDI devices defined in IAC. That is just the tip of the iceberg. Once an input received, you can apply various filters and transformations to the incoming data before you send it out. I'm heavily using these features receiving data from my RM1X (which serves as the main production hub). MIDI clock and transport messages coming from RM1X routed to the USB connected equipment (Novation Circuit, Modal Craft Rhythm) and they are happily slaving themselves to the master, starting and stopping their sequencers when start or stop button pressed on the RM1X. Well, that's not a big deal you might think, but there's more. RM1X can command equipment that is hooked onto it, but the chances are quite high that, you need to change at least the MIDI channel info, before the message hits the other equipment on the output. Sometimes you have to remove unwanted parts of the MIDI messages as well (RM1X very well known to spit out some MIDI gibberish, that can be overheard by external gears). Channel filter and message filter capabilities are here to save your life. I really don't know how anyone can live without this gem in a dawless setup. If you check my gear list, I can tell, that all of my MIDI equipment hooked up to RM1X and controlled perfectly. Combine MIDIPipe with PD (pure data) and you have not limits using your gears. Sure it requires some elbow grease and time to get familiar with it, but I can tell you, you'll not regret the time you invested into mastering this tool.