Ringtone Maker comes with two different interfaces. The first lets you see all the sound files on your device, so you can press on any of them to set it as a ringtone or edit it. If you choose to edit it, you go on to the second interface.
From this editing interface, you can specify exactly what part of the sound file you want to use as a ringtone. The editing system is simple and intuitive, so all you have to do is drag the two beginning and end tabs to set the fragment you want to save. This way, you can extract just the chorus of the song you like, for example.
Ringtone Maker is a simple but powerful audio editing tool that in spite of not taking up much space (barely two megabytes) lets you easily create all your custom ringtones.