​TERPODION. A musical friction-instrument, invented by Buschmann of Berlin in 1816, and improved by his sons in 1832. The principle appears to have been the same as that of Chladni's clavicylinder, except that instead of glass, wood was employed for the cylinder. [See Chladni.] In form it resembled a square piano, and its keys embraced 6 octaves. Warm tributes to its merits by Spohr, Weber, Rink and Hummel are quoted (A. M. Z. xxxiv. 857, 858, see also 634, 645; and l. 451 note), but notwithstanding these, the instrument is no longer known.