itunes 12.1 song into ringtone for iPhone
As Eric says, you need the file to be converted to .aac &amp; have the extension .m4r.

It also needs to be 40 seconds or less in length.

OK, you could pay 50 bucks to do that - or you could do it for free.

Use Audacity to cut to correct length &amp; export as .aac

Then drop the file onto MakeiPhoneRingtone to convert it for the phone.

Drop the result onto iTunes &amp; sync.