03 Jan The Midi In OMNI plugin and the potential for MIDI feedback
The Midi In Omni plugin is very convenient as it doesn’t care from where your MIDI is coming, it will process everything. If you have a single keyboard (or perhaps just a single MIDI pedalboard if you’re a guitarist) then the Midi in Omni is your friend. That’s the main reason we default to including that plugin in every rackspace.
However, if you’re building a more sophisticated rack and in particular you are receiving MIDI via the Midi In OMNI plugin and then sending it through a MIDI Out block, make sure that your MIDI Out block is not an IAC port (OS X) or a virtual MIDI port (such as loopBack on Windows).
Why? Well, when you send MIDI events into a virtual MIDI port, the events will be sent on through that virtual MIDI port’s output. That’s generally what you want if you want to send MIDI events from one application to another. But because the MIDI Omni block listens to ALL incoming MIDI messages, it will receive messages from virtual MIDI ports as well. So as soon as you send out a single event, it will feed right back into the Midi In OMNI plugin and sent out again.
So if you plan to use virtual MIDI ports in your configuration, use specific MIDI In devices rather than the Midi In OMNI.