[Plugin: NextGEN Gallery] Custom music when using [template=extend ]

Hi!
I am loving this plugin. I am using the [ album id=1 template=extend ] to show multiple galleries on one page. The problem I am running into is that I cannot change the background music for each gallery. (I know if I had galleries on separate pages I could use the custom fields option) Is there any way to accomplish this with the [template=extend] shortcut? Please let me know. I really appreciate it.