An unseen effect that really impresses

The magician shows a transparent methacrylate tube through which several strings of different lengths pass.

At the end of each string there is a small bell.

The magician holds the tube with two fingers and asks the spectator to name or stare at one of the bells (at the high end of the rope there are some colored balls for better identification)

Incomprehensibly the chosen bell begins to move and sways while the others do not.

After leaving all still again, the viewer can choose another bell and this time only the last chosen one will be swayed while all the others remain in place.

If desired, the viewer can try and with the power of concentration he can achieve by himself that only the bell he chooses is the one that moves