About multichannel MIDI devices
Multi-timbral MIDI tone 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 multi-timbral devices, you should use separate MIDI Out ports (from the computer MIDI interface to the MIDI In ports) for each device. For example:
There are four MIDI devices that are capable of receiving data on multiple channels. All devices can receive on all 16 MIDI channels.
There is only one MIDI Out from the computer, and all devices are daisy-chained via MIDI Thru to MIDI In connections.
Logic Pro is capable of channelizing MIDI data (routing it to MIDI channels 1 to 16) and sending the channelized data to specific MIDI Out ports. However, in the scenario above, there is only one MIDI Out port available.
In this situation, all data sent on MIDI channel 1 is sent to all four of the daisy-chained MIDI devices. Each device plays the incoming data with the sound assigned to channel 1.
As this example illustrates, MIDI can be separated onto different channels, but cannot be separated between devices, unless you use a multi-output MIDI interface. If you use a multi-output MIDI interface rather than a single-output one, you can specify the MIDI ports on each device. There are no MIDI Thru connections, so Logic Pro can assign and send:
A recording/performance on MIDI channel 1 to port A/module 1
A separate recording/performance—also on MIDI channel 1—to port B/module 2
A further recording/performance on MIDI channel 1 to port C/module 3, and so on with subsequent channels and modules
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.