A lovely piece of performance art, and something of a 'grand illusion' at the same time!
Two rows of bottles, placed at seemingly random spacings, and a man on roller blades with little 'drumsticks' at the sides. As he skates along, the sticks hit the bottles, and cause them to sound.
Every bottle has a different level of liquid inside, and so makes a different note.
Result - Mozart, but not as you have heard it before!