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The name of the MIDI device (port) where the track is routed. This replaces the "MIDI Port" Meta-Event which some sequencers formally used to route MIDI tracks to various MIDI ports (in order to support more than 16 MIDI channels).

For example, assume that you have a MIDI interface that has 4 MIDI output ports. They are listed as "MIDI Out 1", "MIDI Out 2", "MIDI Out 3", and "MIDI Out 4". If you wished a particular MTrk to use "MIDI Out 1" then you would put a Port Name Meta-event at the beginning of the MTrk, with "MIDI Out 1" as the text.

All MIDI events that occur in the MTrk, after a given Port Name event, will be routed to that port.

In a format 0 MIDI file, it would be permissible to have numerous Port Name events intermixed with MIDI events, so that the one MTrk could address numerous ports. But that would likely make the MIDI file much larger than it need be. The Port Name event is useful primarily in format 1 MIDI files, where each MTrk gets routed to one particular port.