This is how you do it to change the volume of a specific audio being played. You cannot just PlaySound(1) and then try to adjust the volume, as it will not work. I tried it and had the same problem until I figured out what was the problem. The solution is that you need to PlaySound(1) to an integer like this:
thunder = PlaySound(music,volume#,0)
Then you can use the command SetSoundInstanceVolume(SoundInstanceID,VolumeValue) like this:
SetSoundInstanceVolume(thunder,volume#)
Then it works.
Have a good night.
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