[Click handler action] If IsMuted is true, unmutes the audio. Then the handler increments or decrements the Volume property by 0.1. The volume levels range from 0.0 to 1.0. Note that the data binding on the TextBlock control takes care of updating the volume display. [Button] 
Volume up, Volume down
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V o l u m e u p , V o l u m e d o w n