Can I send MIDI messages to more than one device via USB? I mean is there some kind of midi hub or midi splitter for usb? Something similar to Midi Box but for USB:
or In other words, have someone seen USB MIDI thru?
The USB protocol always works point-to-point, i.e., it is not possible to have two USB devices that, from the point of view of the computer, behave as if they were a single device.
You have to use multiple USB/MIDI interfaces, or a single USB/MIDI interface with multiple ports, or a separate MIDI splitter device.
Some big interfaces like MOTU Midi Express XT/Micro Express and many iConnectivity devices, do allow you to customize the routing.