Not an answer to your question, but have you tried pressing Ctrl+F10 to tell DOSBox to release the mouse, so you can just close the DOSBox window normally?

Yeah, I tried Ctrl+F10, Ctrl+F9 (close DosBox) and every other Ctrl+Fx combination. I managed to close it just now by opening a cmd prompt in the backkground and killing the process via the taskkil coomand blindly.

Can you confirm these keyboard shortcuts work e.g. to kill DOSBox before you load the game? Just checking to make sure the shortcuts haven't been changed.

Yeah, they work as they should as long as I don't start the game (with music).

It sounds to me like it's a problem with your PC rather than DOSBox. For instance you might have DOSBox set to use a real MIDI device, but due to a bug in your drivers, using MIDI causes applications to freeze. (I'm not saying this is the problem, just an example.)

Perhaps you can try changing some of your DOSBox options, switching various devices on and off until you can figure out which type of device is causing the problem. If you're using digital music, then disabling MIDI shouldn't affect anything.

I presume you've tried other games and they don't exhibit the same problem?

Every other game I set up with DosBox so far worked like a charm, they all share the same standard settings as well, as long as they don't require a different one (e.g. no EMS memory), of course. I'll try disabling any other device than the Soundblaster in the config file, maybe this will help.

Now that I've seen in the DOSBox-x branch that you are using an cue/bin image with ogg files for the music tracks, the problem could be exactly that.
Please re-rip the game to a complete cue/bin that includes the audio tracks and try again.

Edit: and give a SVN built of DOSBox a try (again with a full rip). http://www.dosbox.com/wiki/SVN_Builds

I already tried a full BIN/CUE with actual redbook audio. No difference. The problem also occurs when using digital music, instead of cd audio, so it's pretty safe to assume it's a problem with DosBox and/or the game itself.

UPDATE: It works with the current SVN build of DosBox-X and usind a full BIN/CUE rip (with cd audio instead of OGG files)! 😁

Can you try with a SVN of Dosbox, preferably the Emucr one...

I tried the EmuCR-SVN build yesterday and it worked, too. Strangely, I the tried the vanilla build again and this time the CD audio worked with that one as well. Don't know why it wouldn't work before. However I'll stick to the SVN builds for games that use CD music, because it has working volume control.