Multichannel MIDI devices
Multitimbral MIDI devices can simultaneously receive MIDI data on multiple MIDI channels. Each MIDI channel can be assigned a tone or sound, such as piano, strings, bass, and so on.
To take full advantage of the capabilities of such multitimbral devices, you should use separate MIDI Out ports (from the computer MIDI interface to the MIDI In ports) for each device.
MainStage is capable of channelizing MIDI data (routing it to MIDI channels 1 to 16) and sending the channelized data to specific MIDI Out ports.
In effect, having a multi-output MIDI interface is something like having more MIDI channels. In this scenario, it would be like having 64 independent MIDI channels—with 16 channels per port (A, B, C, and D).
Not only does this allow you to play up to 64 different sounds simultaneously through your tone generators, it also allows full MIDI control for each channel of each device. This becomes increasingly important when arranging and orchestrating such a large number of instrument parts.
If your computer offers several MIDI inputs, you can connect the MIDI outputs of other MIDI expanders and controllers to it.