I do not know what happened, the music was working well all last week. Launched QfG 1 (VGA version) and no music, but sound effects played. The same thing with 2,3, and 4. Anybody know how to get it working again?

I tried reinstalling and I have tried resetting my PC.

If it's happening with all QfG games, try locating the Dosbox folder/settings and deleting them, to make sure it's not having some sort of global setting for which music device to use (although it seems strange, it shouldn't have that). And make sure to keep your saves elsewhere. Originally you could change the music and SFX device in install/setup, but not in the GOG version if you have 64-bit Windows since it'll say it's not compatible.

I recommend asking over at the official Hero-U Discord since no one else has replied here, where the makers of the QfG games and their fans are.

https://discord.com/invite/transolar