Audio Mp3 Editor is an app that lets you edit your sound files using six different tools. The first – and perhaps one of the most useful – lets you trim any audio file and save the result in your device's memory.
Another interesting tool lets you combine two different audio files, play them both at the same time, and create a new file in the process. Obviously you can adjust the volume of each track independently.
Its other interesting tools include an audio converter that lets you change the format of any sound file, plus a tag editor to modify the internal tags for any song. The audio recorder, for its part, lets you do exactly that: record audio using your device's microphone.
Audio Mp3 Editor is a very comprehensive app thanks to which you can make your own ringtones by cropping song clips, change the format of any sound file, and much more.