Can You Play a Tune on Wine Glasses? Benjamin Franklin Built a Machine For It

A finger drawn around a wet glass rim does not slide smoothly but sticks and slips repeatedly, catching the glass and releasing it many times a second, which is the same mechanism by which a bow drives a violin string. Each release lets the glass spring back and the repeated impulses set it ringing at its own natural frequency, so the pitch depends on the size and thickness of the glass rather than on how fast the finger moves. The resulting tone is extremely pure, with very few overtones, which is why it sounds unlike almost anything else and why it is difficult to locate by ear.

Performances on tuned glasses of water existed and were awkward, and his 1761 design fixed the practical problems:

• •Bowls of graded size nested on a single horizontal spindle
• •A treadle turning the spindle, so the player needs no second hand
• •A trough of water beneath, wetting the rims as they turn
• •The rims coloured to indicate the notes, like a keyboard
• •Both hands free to touch several bowls at once, giving chords
• •No tuning by adding water, since the glass itself is ground to pitch

The instrument became genuinely popular across Europe within a decade and attracted serious composers. Mozart wrote for it, including a quintet and a solo piece in 1791, and Beethoven, Donizetti and Richard Strauss all used it. Its tone was described as ethereal and otherworldly, and that quality made it fashionable in a period with an appetite for exactly that. Several hundred instruments were built and touring performers made a living from it. It was also promoted for its supposed effect on the nerves, which is where the trouble started.

Listeners consistently report difficulty telling where the sound is coming from, and there is a reasonable acoustic explanation. The ear locates a sound below roughly a thousand hertz by comparing the time a wave arrives at each ear, and above that frequency by comparing loudness, since the head casts a shadow. The instrument's strongest output sits close to that crossover, where neither cue works well, and the tone is nearly free of the overtones that would supply information higher up. The sustained even quality removes the sharp onsets that the ear also uses. Together those make it genuinely hard to localise, which contributes to the unearthly reputation.

Decline was rapid and the explanations offered at the time were mostly wrong. Reports circulated that the instrument caused nervous disorders, melancholy, convulsions and even death in performers and listeners, and in at least one German town it was banned. Lead poisoning from the glass or from paint has been suggested retrospectively and is unproven. The more mundane explanations are better supported. The instrument is quiet and could not compete in the larger concert halls that the nineteenth century built. It is fragile, expensive and difficult to tune. And playing it wears the fingertips raw. Revival since the 1980s has been led by a small number of makers and players.

A wet finger sticks and slips around a glass rim many times a second, driving the glass at its own frequency exactly as a bow drives a string, which gives an unusually pure tone. Franklin's 1761 design nested graded bowls on a treadle-driven spindle running through water, freeing both hands for chords. It faded because it is quiet, fragile and hard to tune, rather than because it drove anybody mad.