Funny, on my Nexus 4 and Nexus 7, moving a .mp3 into "alarms", "notifications", or "ringtones" won't make them appear as sound files when in settings under "Sounds" or in the clock app under alarms. In order to have them show up, I have to use a root file explorer and navigate to a specific root folder that would be inaccessible to the average user.
Not to mention updating my ROM (CyanogenMod for example) will revert this root folder back to normal. So for people who like to run nightlies, like myself, you have to constantly be putting in these audio files into that root folder every day.
On iOS, I could simply export out a song from GarageBand and it would do all the other work automatically.