In north america the appalacina dulcimer is envolved from european Scheitholt or Hummel from north Germany and is popular in the folcmusic. The Appalachian Dulcimer has 4 strings. The both high strings are tuned the same, the others are a quint and octave to the base note.
A typical tuning is d - g - d' - d'
The frets are diatonic.
Like a zither on a table or on the legs of the player, the strings could be plucked or striked. You touch just one string or all three together for example with a bamboostick. Typical it is played with a bottleneck, to slide between the frets. Cause the tuning in quints you can play with open strings and bordun or accords.