1. Be sure to enable "Inter-Application MIDI" in FreeMIDI. This will enable the Trigger plug-in to be "published" as a freemidi input device.
(a) Open the FreeMIDI Setup.
(b) From the FILE menu, choose "FreeMIDI Preferences".
(c) Place a check in the box next to "Inter-Application MIDI"
(d) Close the Preferences window, SAVE Freemidi and Quit.

2. In Digital Performer, insert a Trigger plug-in on an audi track (see page 694 of the DP3 guide for more info on Trigger)

3. Record enable a MIDI track with a device, channel & patch assigned.

4. Adjust the Trigger plugin's parameters, such as Threshold, monitor the midi track to achieve the correct response.