https://www.assetstore.unity3d.com/en/#!/content/83065
This tool will allow you to export all the snapshots attached to a Unity Audio Mixer with one click, retaining volume settings. That means that you can mix new versions of songs from the Asset Store* and export the results to use in your game. Music can match YOUR game and YOUR mood.
* Composers will have to provide the layers, one for each instrument/sound, and should set up the demo scene with a ready-to-use Audio Mixer. It’s easy to set up the Mixer if they don’t, but they should. Message your favorite composers and ask them to make their music compatible with the Batch Snapshot Exporter (link them to this thread!). Best part? They can include this tool in their packages FOR FREE!