With the introduction of iTunes 12.7 in September 2017, Apple drastically changed the way custom tones are handled. Removing the “Tones” section of your iTunes library broke the ability of apps like Fission to automatically add custom tones to your iOS devices. However, it is still possible to use iTunes to add custom tones to your iOS device.
To get custom tones on your iOS device with iTunes 12.7 and up, make sure you have Fission 2.4 or higher, then follow these simple steps.
1. Create your ringtone in Fission.
Open your desired audio in Fission, then crop it down. The file must be 40 seconds or less in length, and you'll likely want a very short (1-2 second) file for texttones.
2. Select “Save as iPhone Ringtone”.
Fission will automatically save the custom tone to your Music folder (in ~/Music/Tones), and open that folder.
3. Navigate to your iOS device in iTunes, and click the Tones section.
4. Drag and drop the file into Tones.
iTunes should now sync the file directly over to your iOS device.
Once the file is on your iOS device, it's ready for use. Set the sound as your global ringtone or texttone in the Settings app (Sound section), assign it to a specific person in the Contacts app, or use it for alarms or timers in the Clock app.
Storing Tones on your Mac
It's worth noting that iTunes no longer saves new custom tones in its iTunes Music Library. Because of this change, we recommend manually saving a copy of these files on your Mac to ensure you have a backup of these files. Fission automatically saves your custom tones to your Music folder, in ~/Music/Tones, so you can simply keep them there.