Smule is a social singing app that allows users to sing and make music with friends and people from around the world. The platform offers features such as karaoke singing, solo and duet performances, and even group collaborations. Users can also add audio effects and visual filters to their performances and share them with the community. Smule provides subscription options that may include access to a larger music library, enhanced audio effects, and the ability to sing offline, among other premium features.