Hammered Dulcimer

Dulcimers may have originated in the Middle East, probably during the first millennium A.D. It is possible therefore that the instrument could have been brought to Europe from the Middle East during the Crusades. Other research puts the origin near the end of the Middle Ages, in Europe, holding that the earlier medieval paintings and statues depict psalteries or dulcimer-like instruments without a central bridge. Psalteries though are plucked rather than hammered. Whatever the historical origins, similar instruments have spread around the world.

The dulcimer is also a direct ancestor of the piano:

Toward the end of the 17th Century and beginning of the 18th, harpsichordists were complaining to instrument makers about the harpsichord's lack of dynamic responsiveness. Pushing the keys harder or softer does not give you a stronger or softer sound, and pushing too strongly can damage the instrument. A dulcimer, on the other hand, is capable of playing with dynamics. Strike softly for soft sounds: strike hard for loud. Mechanizing the hammered dulcimer action and linking it to a harpsichord keyboard gives you a keyboard instrument that can play soft "piano" and loud "forte". A piano (pianoforte) could be described as a mechanized hammered dulcimer operated by keys derived from a harpsichord. The Italian Bartolemeo Cristofori designed and made such an instrument: Hammers responsive to keys would strike the strings, instantly rebound, and strike with varying force - producing volume that varied at the will of the player.

The zither group of instruments are more modern than the dulcimer. They have fretted melody strings and no central bridges, are plucked and not struck. Both hammered dulcimers and concert zithers, like psalteries, harpsichords and pianofortes, do have free strings running parallel to the soundboard. Harps, in contrast, have free strings perpendicular to the soundboard.