I have done searches on the Internet and found numerous reports of this problem. Please look for yourself and decide if there is a problem or at least tell us how to fix this situation.

Access this URL : http://www.mamarocks.com/cats.htm in FF20 lets the background music associated with it play. However, accessing the same URL in FF21 and newer results with the webpage being displayed but the music associated with it does not play. Microsoft Windows Media Player plugin is installed but is not selectable from the file type play selection. The Quicktime Player plugin is also installed. Selecting that or Windows Media Player to handle midi files has no effect on the behavior. I don't believe the plugins are at fault but rather something in how Firefox handles background file use that has changed. I have done searches on the Internet and found numerous reports of this problem. Please look for yourself and decide if there is a problem or at least tell us how to fix this situation.