Hi there
I believe ".wav" is currently the only supported sound file type, but you can't save it properly with Windows Sound Recorder, I believe (plus it's a bizarre sound quality setting - not one of the regualar "levels" of sound, I think...).
If you're asking about how to add sound to a level, I think you'll probably get a more informative answer, asking this question in the "Editing Forum"; that said, if you want to know how to play sounds in JK & MOTS then read up on the "Sound" verbs, in SaberMaster's DataMaster - that has all the necessary flags/settings/parameters that your souund will ever need to play in-game
Hope this helps (at least a little way) to solving your problem...
-Jackpot
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