Having developed several glass harmonicas, in March 1790 Chladni announced the invention of a new instrument that he called the euphone. Resembling an organ and piano, and unlike the harmonica from which it was derived, the euphone was composed of glass strips (as opposed to bowls or vessels). Each strip was a different length and generated a different tone. Chladni discussed the relationship between the lengths and the tones in his Entdeckungen über die Theorie des Klanges.

The forks give the notes cⁱⁱⁱ, c^iv, d^iv, e^iv, f^iv, the 11th harmonic of c¹, the 13th harmonic of c1, aiv, the 14th harmonic of c¹, b^v, and c^v (cⁱⁱⁱ and c^v have vibration frequencies of 1024 and 4096 respectively).

These forks are constructed to prove the following law:

The Stimmeinstellungszeichen, literally “voice disposition indicators,” are metal shapes about 10 cm in diameter. Polished brass wire is bent to form abstract curves and lines. The linguist Eduard Sievers invented them to support his system of sound analysis (Schallanalyse).

The set of eight tuning forks was acquired by the Science Museum, London, on the closure of the Physics Department of the Royal Naval College, Greenwich. The box is marked “Standard Set of Tuning Forks.” A handwritten note in the Science Museum’s technical file T/1968-634 states that no mention of this particular box of forks can be found in the Museum’s copy of König’s 1889 catalogue (Koenig, R. Catalogue des appareils d’acoustique).