A free app for Android, by Fun Muzik.

Super Audio – Audio Editor is a tool that lets you edit and combine multiple audio files into one. This is really useful for people who want to create their own songs or audio songs. This app lets you do many things, such as change the pitch, add effects, cut the songs, and merge the songs into one file.

This app is really easy to use, and all you need to do is select a file and then apply an effect on the selected file. 

This app is free to use, and there are no in-app purchases. You can download this app and use it without any restrictions.