mp3 has licencing issues
Ogg and MP4A has none.
Best use a converter for mp3/mp4 to Ogg, cause these two have been deprecated anyway in AppGameKit I believe
So, as long as the music mp3/mp4 has no licencing attached to them which has must DO's and Donts on them then suppose that's fine.
Public Domain music and attribution is best ones
Please read to give yourself the idea of mp3/mp4 formats -
http://mp3licensing.com/help/developers.html
Good music for free I have found this to be a good one for funky music and sounds
https://incompetech.com/music/royalty-free/music.html, please mention the author of the music
in your game credits - in this case its Kevin MacLeod
eg credit info to give
"Laser Groove" Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 3.0 License
http://creativecommons.org/licenses/by/3.0/
Hope this helps
Damian