The standalone version of GDT worked fine so far, but since I switched to the Steam version today I got no sound/music anymore. Other apps and games (FTL) play nice, so I am not sure what might cause this. I already tried switching sounds off and back on again within GDT but to no avail.
Is your Steam playing with no sounds? I don’t know if there’s an option for that though… Nice Avatar. 
I am not aware of a Steam wide mute button either, and other games play fine. It’s the Mac version btw.
Thanks 
Yay for stuff that happened here. Yay.
Have you checked the in game settings to make sure music and sound effect are all on and that volume is turned up?
I tried playing with the sound settings in GDT but that didn’t seem to have any effect either.
It seems to work now after updating Steam, but my previous save game apparently got lost in the cloud, though that’s probably more a problem with Steam itself…