The common theme chosen by the Federation of European Postal Services is "national music instruments". While the zither is synonymous with an Alpine tradition, it has gained a foothold in modern ensembles as well.
The zither is a musical string instrument, consisting of many strings stretched across a thin, flat body. It is played by strumming or plucking the strings, either with one's fingers, or using a tool called a plectrum. Like a guitar or lute, a zither's body serves as a sound box, but unlike them, a zither has no neck. The number of strings varies, from as few as twelve to more than fifty.
The term "zither" organologically refers to a broad family of Eurasian musical instruments, but in modern usage most commonly refers to one of three specific instruments: the concert zither and its variant the Alpine zither and the fretless (or "guitar") zither.