It works perfectly for me using mp3s creating by iTunes2.
Maybe you have to change slightly the types defined in the array:
either by adding @"MP3"
or using the HFS file type (I don't know the exact file type, as I have no mp3 on OS9:
Try press the space bar, it could show the controller.
Or use what I did, show the controller at anytime:
// Display the controller taking in account the controller's size
[movieView showController: YES adjustingSize: YES];
Your code to resize the window at magnification 1.0
// Make the movie acccepts key and bring it to front
// to allow play in background
[movieWindow makeKeyAndOrderFront: self];
// Ensure that the controller redisplays after reopening a file