Source
From the announcement:
Syrinscape is an easy to use app that adds evocative ambient background sound and a movie-like soundtrack to your gaming experience, conjuring every aural landscape imaginable, from ethereal forests or dank, vermin-filled dungeons to the spooky depths of the underworld.
Syrinscape uses editable and adaptable libraries of sound files – SoundSets – to ‘improvise’ soundscapes. Thus giving you a great degree of control over what you are hearing, while requiring almost no interaction from the user while it runs. Syrinscape sounds amazing!