Sound is being worked on as we speak for Parchment and normal inform.
In the mean time though I’ve made an extension and custom interpreter that makes it work just fine. You can see it here (documentation in second post):
You’ll need to download an old version of Glulx Entry Points, which is available here:
There are some annoyances (you need to put .ogg files in one folder for it to compile and .mp3 files in another to get it to play online) but there are at least two games out there using it now with working sound. Here is a working example by Wade Clarke:
Edit: By the way, sound should be working offline, such as in the inform interpreter. That’s kind of weird if it’s not already doing that.