Hi:
You can try looking in System Settings> Window Behavior> Window Rules that is if you have that in your Applications Menu.
You can try this but I can't guarantee it will work.
Press ALT+F3 and go to: Advanced - Special Application Settings - Geometry
If that doesn't work the only other thing I can think of is to try holding down
Ctrl & + at the same time.
If not Rhythmbox for MP3 might be another alternative to consider.
http://sourceforge.net/projects/rhythmbox/
https://help.ubuntu.com/community/Rhythmbox
https://wiki.debian.org/Rhythmbox
