Now that I've completed the first draft of my movie, I find that I want edit bits and pieces here and there, but I don't want the music track to be affected. How can I do this?
Select the first event on your music track. Right click to bring up the context menu and select "Select events to end". This should highlight the all the events on the track. Now right click on the first event again and select "Switches->Lock". This will lock all the events on the music track. You can now edit the rest of the video and the music will not move or be cut.