That was easy

It's, err, sorted.
Sound is working.

I haven't tested for systems without OpenAL yet. I think I have enough checks to stop an outright crash but I need to be sure.
I also haven't added the "sound effects on/off" line in the options, which needs doing as not everyone likes retro beeps and whistles. Might add a volume control to that as well, will see.

But yeah, the game is pretty much finished. I'll make a video later demonstrating the sounds and um, guess I'll release it once I've checked the OpenAL stuff and added that line to the options screen.