Rusty
It will not save any changes in GM,playing or paused. Everything works as far as muting, volumes, etc,while playing. As soon as I save it with the same name or different one, the changes are not saving.

I use midifiles quite a lot and have to use the files where I can use the "Lead" track to mute. Unfortunately, there are files that have a double instance of lead, and other changes that can only be handled by the GM window.

I have been trying to think of a work around, but haven't yet.