What is a mountain dulcimer?
A mountain dulcimer is a fretted instrument with a soundbox that runs almost the entire length of the fretboard. One usually plays a mountain dulcimer by laying it across one's lap. Sometimes, a player frets only the high-pitched string (or pair of strings) with one hand while strumming all strings with the other hand; in this case, the other strings provide a drone accompaniment. At other times, a player frets any/all strings with one hand pick the strings with the other hand.

A mountain dulcimer usually has either three or four strings. If the instrument has four strings, two of the strings usually are positioned closely together, are tuned to the same pitch, and are played as one to provide greater volume. A mountain dulcimer usually is either hourglass-shaped or teardrop-shaped.

Mountain dulcimers also are known as Appalachian dulcimers or lap dulcimers.

The mountain dulcimer I built

A teardrop-shaped mtn dulcimer
Click on image to enlarge
I built the four-string mountain dulcimer pictured here, from scratch. It is constructed entirely of walnut (from a piece of lumber that had been laying in a farmer's barn for 30 years). I hope to build more mountain dulcimers in the near future.

What is the difference between a hammered dulcimer and a mountain dulcimer?
The best answer I've heard to the question is this: If you drop a hammered dulcimer on your toe, it hurts a lot more than a mountain dulcimer would.

For a more useful answer, compare the instrument description and image on this page to those found on the hammered dulcimers page.