A free program for Android, by beka.

The MP3 cutter app will allow you to use the most enjoyable portion of your MP3 song as your ringtone, notification, alarm, or background music. Since you can’t play the entire song and you only want to use the chorus part or any part of the song that you prefer, this app will help you do so! 

This is very easy to use. Just download the app, choose a song, choose the song part which you want to use and start cutting it. The cut results are now more accurate and kept in “sdcard/media/audio/” now once you save them.