Zither
From Conservapedia
A zither is a small stringed musical instrument that has its origins in the folk music traditions of Eastern Europe.Like many string instruments, it has many variations and is generally considered to be a broad term for that genre of instrument.
Someone who plays a zither is known as a zitherist.
Outside Eastern Europe, the zither is known as the instrument used for the memorable theme tune of the film The Third Man, set in post-war Vienna.