ok i just found this in another thread, it doesn't say how to delete but shows a fix to not seeing ringtones on your phone, but it still hasn't worked for some.
This assumes you are starting with an AAC file that your renamed from M4a to M4r
There is a ringtone type assigned to iTunes “.M4r,” executing this ringtone type does a few things. The first time you ever execute one, it adds a Ringtone directory to your iTunes Music directory structure IF you have iTunes managing your music.
It also adds the ringtone to the Ringtone tab within the iPhone section of iTunes.
In 7.4.0, that’s all that was needed. The M4r files synced back and forth to your iPhone.
In 7.4.1 iTunes made the .M4r extension useful for “registering” a file as a ringtone, but also made it “incompatible” with syncing.
What file extension can ALWAYS be synced to any iPod like device? .M4a
Thus renaming the .M4r files that are now REGISTERED and LOCATED IN RINGTONES DIRECTORY to a .M4a extension bypasses the incompatibilty error trap that was added in 7.4.1
Someone please verify these steps and correct them if wrong…since I think folks will benefit from a stepwise procedure. Lettered steps are ones i’ve used for cleanliness an may not be required
1. Confirm iTunes is set to import to AAC 128
2. If the “to-be” rington is not currently AAC, convert it by right clicking
3. Delete the new aac file from the library ONLY
4. Locate the file and Move it to your desktop
5. Rename the file from xxxx.m4a to xxxx.m4r
6. Double Click on the file
7. Return to iTunes and confirm it is now in the iPhone ringtones tab, but no not Sync
8. Locate the file in your iTunes Music/Ringtones Directory
9. Rename file from xxxx.m4r to xxxx.m4a
10. Sync! All should be well.
One specific confirmation request for the community. Pleae confirm that there is NO NEED to double click on the newly renamed M4a file located in the Ringtone directory. It seems this messes things up, but I’ve seen it listed several times before.