This MIDI effect app for Audiobus 3 allows you to filter out MIDI messages on specific MIDI channels. Furthermore, you can remap the channel to a different value.

+ Filter out messages on specific MIDI channels
+ Remap channels
+ Use multiple instances of this effect in Audiobus

NOTE: This app requires Audiobus 3. Insert it into one or more MIDI effect ports to affect the data going through the respective pipelines.