I'd like to set 10.10 to open MP3 files in Muinshee when I open them from a file manager. I don't really like Totem very much, and opening all of Banshee is a little bit too heavy for just playing a one-off audio file I grabbed from the web, or a song that one of my friends recorded and then sent to me over Empathy.
2 Answers
Right click over a file, properties, there is an "Open With" tab, set the default application there.
You can also go to System > Preferences > Preferred Applications and do it from there.