Glass armonica
Instrument of rotating glass bowls rubbed with moist fingers (B. Franklin).
What it means
The glass armonica is an instrument of graduated glass bowls arranged on a horizontal axis and set in rotation by a pedal. The players touch the rims of the rotating bowls with moistened fingers and thus produce tones by friction. The sound is delicate, floating, and hard to locate.
Musical use
The glass armonica was invented in 1761 by the American statesman and inventor Benjamin Franklin, who developed the idea of playing on glasses into a device resembling a keyboard instrument. It became popular in the late 18th century; Wolfgang Amadeus Mozart wrote his Adagio and Rondo K. 617 (1791) for it. Because of its delicate construction and difficult technique it lost importance in the 19th century but is cultivated again today.
The glass armonica should be distinguished from the glass harp or musical glasses, in which single glasses are filled with water and rubbed, and from the harmonica or harmonium, which despite the name are entirely different sound producers. It belongs to the idiophones, since the sound arises from the glass itself.
Performance practice
Keep your fingers clean and evenly moist for the glass armonica, without soap or grease, otherwise the bowls will not sound. Touch the bowls with gentle, even pressure and calm movements; the tone arises slowly and needs patience.