Several years ago I wondered whether this obscure format could be played back
using a free audio decoder (I downloaded such a file that according to its
metadata was encoded in 2000):
https://trisquel.info/en/forum/voxware-metasound-playback
I was pleasantly surprised yesterday to find out that the file I downloaded
played back perfectly on Hyperbola GNU/Linux using MPlayer and mpv without
using non-free binary codecs.
Apparently, FFmpeg developed an encoder for this format in version 2.2 (which
was released in 2014), probably 10+ years after this format was commonly used
for distributing online audio, and both MPlayer and mpv apparently use
FFmpeg's decoder to playback the audio.
You can find a few samples in this format here to see if your video player
supports it:
http://samples.mplayerhq.hu/A-codecs/VoxWare/
