The singing of the wine glass

  As you rub your finger on the rim, your finger first sticks to the glass and then slides. This stick and slide action occurs in very short lengths and produces a vibration inside the glass which in turn produces a sound. As soon as the first few vibrations are produced, the glass resonates. 

That means you’re causing the crystals in the glass to vibrate together and create one clear tone.

The pitch can be changed by adding to or subtracting from the amount of water in the glass. 

The volume can be changed only a little bit by increasing or decreasing the pressure from your finger. 

The movement of the match is caused by a sympathetic vibration. Because you added equal amounts of water, the second glass vibrates at exactly the same frequency as the first. The sound waves produced by the first glass travel in every direction. When those sound waves reach the second glass, the glass begins to vibrate as well and the match moves.