Zmachine and Glulx: can multiple sounds be played at once?

I don’t recall even seeing any working examples of SONG.

In case anyone’s interested, I’ve sucessfully added AIFF, OGG, and MOD playback to Unix Frotz. I’ve decided to follow the behavior of Windows Frotz and Sfrotz in how things are played: Only one of OGG or MOD may play at a time. AIFFs are allowed to play along with OGGs or MODs. I’m not finished yet. I’m having a problem getting simultaneous sounds mixed.

See for the code.