Invented by Benjamin Franklin, the glass armonica (or glass harmonica) consists of a series of glass bowls of varying sizes arranged on a rotating spindle. The player touches the rims of the rotating bowls with moistened fingers to produce haunting, ethereal tones. It became wildly popular in 18th-century Europe, with Mozart and Beethoven both writing music for it. However, a strange legend arose that the instrument could cause madness, melancholia, and even physical illness in both performers and listeners. Some modern historians suggest this 'glass armonica madness' might have been lead poisoning, as the glass used at the time had high lead content that could be absorbed through the skin. Others believe the high-frequency vibrations simply unnerved people. Though it fell into obscurity for over a century, the instrument is still used today in film scores to create 'magical' or 'unsettling' atmospheres.