Sound.Volume
From Xojo Documentation
Property (As Integer )
aSound.Volume = newIntegerValue
or
IntegerValue = aSound.Volume
Supported for all project types and targets.
or
IntegerValue = aSound.Volume
Supported for all project types and targets.
Controls the volume of the sound.
Notes
The range is from 0 to 100; 0 mutes the sound and 100 plays the sound at the "normal" volume set in the computer's volume setting. Default is 100.