Quote:

In the pop up box I could see QuickTime but it was grayed out.


That's normal. It just means that QuickTime is selected by default.

You may try this little test.

1. Assign the DLSMusicDevice to an instrument track.

2. Create an empty region of 4 bars on this track.

3. Open the region in Piano Roll and insert a note at bar 2.

4. Start the sequencer and you should hear the note playing.

By default the note will play with piano sound. Now, if you create a program change message in the Event List at bar 1, the note should play with the corresponding GM instrument.

Note: personally I don't advocate using Logic and DLS for handling Standard Midi Files, but just wanted to explain that it's possible.