If you have a standard Midi file created in a non MOTU application, it may not show up as a readable document in Performer or Digital Performer. There's a handy utility included with Performer and DP that let's you convert these to a readable state. This utility is called Midi File Converter, and can be found in the Performer Folder within a folder called "Extras". It's easy to use. Just double click on Midi File Converter, and it will ask you to locate a Standard Midi File. Midi File Converter opens it spits it out in a readable form, so that when you choose file>open in Performer, and select "all readable documents" at the bottom of this open dialog box, the SMF will show up.