The Mountain Dulcimer is an American instrument. It is a stringed instrument with frets, in some respects similar to a guitar. The dulcimer has a long, narrow resonant cavity or soundbox. The dulcimer lays on you lap. Then you can fret the strings with one hand while strumming or picking the strings with your other hand.

We are told the Mountain Dulcimer originally was a teaching instrument for elementary-school-age students. In the cabins of Appalachia, Mom would keep a dulcimer hanging on the wall near the fireplace, and would take it down to teach the children as soon as they were old enough to count to 10. When the children showed any talent for music, then they would "graduate" to a "real" instrument, such as a guitar, banjo, or fiddle.

The Mountain Dulcimer has a modal fretboard. That is, the fretboard has only those frets necessary for playing a modal scale across one octave on any single string beginning in the open position. Traditionally, this modal scale was the Mixolydian scale, but modern dulcimers usually have "one extra fret" for playing the Ionian or major scale on a single string from the open position. Of course, one can begin a scale from a position other than the open fret to achieve any of the "church-mode" scales, including Ionian, Aeolian, and Dorian. Furthermore, the dulcimer typically has three strings, and these strings can be tuned differently to achieve other notes.

The Mountain Dulcimer typically has three strings. As you hold one on your lap, typically the string farthest from you is tuned lowest, the string nearest you is tuned highest, with the string in the middle tuned in between. The string closest to you is called the "melody string" and traditionally might be the only string fretted to play a song while the other strings simply droned in their open positions to achieve a sound something like a bagpipe band. The dulcimer is sometimes strung with a double melody string, with two strings physically close together and tuned identically, similar to how a mandolin is strung. Of course, this simply makes the melody-string notes twice as loud as notes of the other strings.

The modern style of the Mountain Dulcimer includes fretting all of the strings to play chords. This increases the complexity of the music that can be performed. This style emerged and grew in the 20th century, leading to dulcimer experts including David Schnaufer. David Schnaufer was the first winner of the U.S. national championship at the Walnut Valley Festival.