SoundSource is described as 'Control volume and audio output per application, apply individual equalizer settings, and access advanced sound features from the menu bar on macOS' and is a Volume Control tool in the audio & music category. There are more than 10 alternatives to SoundSource for a variety of platforms, including Mac, Windows, Linux, iPhone and iPad apps. The best SoundSource alternative is EarTrumpet, which is both free and Open Source. Other great apps like SoundSource are FineTune, Volume2, BetterAudio and Background Music.