The carriers tend to hide how to make ringtones so you’ll buy them, but there are a few good resources to make your own. This one is from FunMobile…How do I make mp3, m4a/AAC, wav ringtones? How do I make a mmf ringtone? How do I make a qcp ringtone? How do I make ringtones from CD? How do I make a polyphonic (midi) ringtone? Tons of screenshots and how to action. Link.
HOW TO make ringtones