How did Apple make information ringtones without jailbreaking?

The steps to change the ringtone are as follows:

1. Open itunes and select File-Add File to Library in the menu bar

2. Select the song to be used as ringtone and click Open

3. The song will appear in Music of Library. Right-click the song and select Show Introduction. -"OK"

p>PS：iphone rings within 4 seconds

5. Right-click the song and select "Create ACC Version"

6. A file with the same file name but less than 4 seconds appears

7. Right-click the newly created song, select "Show in windows

explorer" and put "m4a" Select "Yes" in the pop-up window

8. Check: Find "Preferences" in the menu bar "Edit" of "itunes", open the box in front of "Ringtone" in "Common"-"Source", and then "OK". You can see ringtones in the database. Open ringtones to see whether your files have been converted into ringtones. Then open iphone in Devices to select ringtones, tick the item "Synchronize ringtones", select "All ringtones" or "Selected ringtones", and then select "Synchronization".