Ports In the MIDI Recording Tutorial, you learned to record using Ports, which play the MIDI events on a track according to their original record channels. This is possible because Metro records each MIDI event with its own channel information and uses this channel assignment when playing back through a Port. Since you can record up to sixteen channels simultaneously on a single track, Ports can play up to sixteen channels per track. Ports can also be defined as audio devices. Ports are automatically named according to the Record Port assignment (in the MIDI Setup and Digital Audio dialog boxes reached through the commands in the Setup menu). You can’t customize them within Metro. If you have only one device in your MIDI setup and are not interested in using Metro Outputs to control various track parameters, you’ll probably want to record using Ports.