Literally mad

"The glass harmonica, also known as the glass armonica, bowl organ, hydrocrystalophone, or simply the armonica (derived from "harmonia," the Greek word for harmony), is a type of musical instrument that uses a series of glass bowls or goblets graduated in size to produce musical tones by means of friction" - Wikipedia

This instrument was popular in the early 18th century but not much past it apparently due to superstitious beliefs about people going mad from playing it. A German musicologist by the name of Friedrich Rochlitz noted

"The harmonica excessively stimulates the nerves, plunges the player into a nagging depression and hence into a dark and melancholy mood that is apt method for slow self-annihilation. If you are suffering from any nervous disorder, you should not play it; if you are not yet ill you should not play it; if you are feeling melancholy you should not play it."

Less superstitious theories attribute the the dangers of playing it to lead poisoning...who knows...

Sounds cool!