The iTunes Store offers a variety of ringtones that you can purchase for your iPhone. However, you may want to create a custom ringtone from a song imported from a CD or purchased on a music download website. The iPhone supports ringtones up to 40 seconds long, and iTunes has the tools you need to create a custom ringtone of a suitable length.
Launch iTunes and play your song to determine a start and stop point for the ringtone. Make note of the start and stop times in seconds.
Right-click the song, then select "Get Info" on the context menu. Click the "Options" tab and tick the check boxes for "Start Time" and "Stop Time." Enter a start time and stop time for the ringtone in the applicable input fields and click "OK." Right-click the song again and select "Convert Selection to AAC" to create a clip using the selected start and stop times.
Right-click the cropped audio clip and then select "Show in Windows Explorer." Right-click the file in the Windows Explorer window and click "Properties." Change the "M4A" extension at the end of the file name to "M4R" on the "General" tab and click "OK." Click "Yes" when Windows prompts you to confirm the file extension change.
Drag and drop the M4R file from the Windows Explorer window to your iTunes library window. Click "Ringtones" on the left pane on iTunes to view your new ringtone.
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