Yes, the MIDI OUT port on the Keystation 88 can function in two ways:

1. As the controller's MIDI out - they keys and knobs send out this port (factory default)

2. As a computer MIDI out - "USB MIDI" - this functions as a USB MIDI interface, the output will be what the computer sends to the USB MIDI out, not the actual keyboard's output. You can use this mode to hookup an external sound module to the computer.

To switch between modes, press the 2 buttons on the upper-left side of the controller that have “MIDI Out from USB” labeled under them to toggle between modes.