AudioMixer is a Unity script written in C# that attempts to implement an audio mixer with channels. In Unity, the most typical way to control audio was though priorities, which could be set in a sound’s properties. There was never a built-in system to relay audio to a specific channel.
AudioMixer implements audio channeling via a script with the same name that is attached to a GameObject. Entities in your game that need to play a sound (or music) can call AudioMixer to play a sound in a specified channel of your choice. Notice that this is not a Unity extension and thus does not make audio channels a built-in feature in Unity.
AudioMixer was made for music and 2D sounds in mind. This is not recommended for 3D sounds. 3D sounds require a location, which would be too cumbersome to implement in AudioMixer.
You can read my reason for starting this here.
You can grab AudioMixer on the link below: